Glossary
60 terms, each answered in the first sentence and grounded in a worked small-business example. No vendor spin.
A cloud phone system runs a business's calls, numbers and voicemail through software hosted on the provider's servers rather than an on-site box. Setup, routing and new numbers can all change from an app in minutes.
A codec compresses voice into digital data for sending over the internet. Then it decompresses that data back into sound at the other end. The codec used affects call clarity and how much bandwidth a call needs.
A DID is a phone number that connects straight through to a specific person, extension or line without needing a receptionist to transfer the call. Many numbers can still share the same underlying system.
E.164 is the international standard format for phone numbers. It always starts with a plus sign and country code (for example +14155552671), so systems worldwide can dial the same number without ambiguity.
Jitter is the variation in delay between voice data packets arriving over the internet. High jitter makes calls sound choppy or robotic even when overall internet speed looks fine.
Latency is the delay between someone speaking and the other person hearing it. Under about 150 milliseconds it is unnoticeable, but higher latency causes the awkward talking-over-each-other feel of a bad video call.
The PSTN is the traditional copper and fibre phone network that has connected landlines for over a century. VoIP systems still reach PSTN numbers, but the call typically converts to internet data at some point in the journey.
SIP is the signalling standard that sets up, manages and ends VoIP calls. It tells devices how to find each other and start talking. It is the plumbing most business phone systems and softphones run on.
A virtual phone number is a phone number not tied to a physical phone line or a specific desk. Calls can route to an app, a team, or several devices at once. It works anywhere there is internet.
VoIP turns your voice into data packets and sends calls over the internet instead of a copper phone line. It works over any broadband, wifi or mobile data connection, and it underpins almost every modern business phone system.
An area code is the prefix identifying the geographic region a phone number is registered to, like 415 for San Francisco or 0161 for Manchester. It is the first thing many callers notice about a number.
Caller ID shows the recipient the number, and sometimes name, of who is calling before they answer. Businesses can set what displays, which affects whether customers recognise and pick up the call.
A local number carries the area code of a specific city or region. It signals to callers that a business is based there, even if the team actually works from somewhere else entirely.
A mobile virtual number looks and dials like a standard mobile number, but runs through an app rather than a physical SIM. That lets a business keep a personal phone separate from a work line on one device.
A national number is not tied to any specific city or region. It gives a business one number that works the same way no matter where a customer is calling from within the country.
Number porting moves an existing phone number from one provider to another. That way a business keeps the same number customers already know, while switching to a new phone system underneath it.
A toll-free number, like an 800 or 0800 number, lets callers reach a business for free. The business pays for inbound minutes instead of the customer. It signals scale and customer-friendliness.
A vanity number spells a memorable word or phrase on the keypad, like 1-800-FLOWERS. That makes it easier for customers to remember and repeat than a random string of digits.
An auto-attendant is an automated virtual receptionist that greets callers and directs them to the right extension or department. It replaces the need for someone to answer and transfer every call manually.
Business hours routing automatically changes how calls are handled depending on the time of day. It sends calls to the team during opening hours, and to voicemail or an after-hours message once the day ends.
Call forwarding sends an incoming call from one number straight to another. It lets a business number ring a personal mobile, a different team member, or another office, without the caller knowing anything changed.
A call queue holds incoming calls in order when every available team member is already busy. It plays hold music or updates until the next person becomes free, instead of giving the caller a busy signal.
Call routing decides where an incoming call goes: which person, team or device rings, and in what order. A business sets up these rules in advance, rather than a receptionist deciding case by case.
An IVR is the automated "press 1 for sales, press 2 for support" menu callers hear before reaching a person. It lets a small team route calls to the right place without a live receptionist.
A ring group is a set of phones or team members that all ring together (or in sequence) when one shared number is called. Any available person can pick up, rather than the call depending on one fixed line.
Simultaneous ring makes several phones or devices ring at the same time for one incoming call. Whichever one gets answered first takes the call, and the others stop ringing.
A warm transfer briefly connects the receiving team member with the caller's original contact, before handing the call over. That way, context passes along, instead of the caller having to repeat their story from scratch.
A2P 10DLC is the US carrier framework that lets businesses send automated or bulk texts from a standard 10-digit number. Registering a business and its messaging use case with carriers is required before high-volume texting works reliably.
Business SMS is text messaging sent and received from a company's main phone number rather than an owner's personal mobile. Messages land in a shared inbox the whole team can see and reply to. It's the same number customers already call.
A long code is a standard 10-digit phone number used for both calls and texts. It's the same format as a normal business or mobile number. It is the default number type behind almost all business SMS today.
MMS is a text message. It carries a photo, video, GIF or a longer body of text (over 160 characters), instead of plain text alone. It travels over the same business number as SMS, just with an attachment.
A short code is a 5 or 6-digit number used to send very high volumes of text messages. Think appointment reminders from a large chain, or one-time passcodes. It is separate from a business's regular 10-digit phone number.
SMS opt-in is a customer's recorded consent to receive text messages from a business. It's usually gathered through a checkbox, a reply keyword or a signed form. It protects the business if a carrier or regulator questions why a number is texting someone.
A call log is the record of every call made or received on a business number. It shows who called, when, how long it lasted and the outcome. It is the basic audit trail behind a phone system.
Call recording automatically saves audio of business phone calls for playback later, used for training, dispute resolution and quality checks. Recordings are usually stored in the cloud and searchable by date, caller or team member.
Call screening lets someone see who is calling. Sometimes they can hear an automated prompt asking the caller to state their name, before deciding whether to answer, forward or send the call to voicemail.
A cold transfer sends a caller straight to another person or team without speaking to them first. This differs from a warm transfer, where the receiving person is briefed before the call arrives. The caller repeats their reason for calling to whoever picks up.
A conference call connects three or more people on a single phone call at once. It works either by merging separate calls or by dialing into a shared access number and code. It is standard on most business phone plans.
Do Not Disturb silences incoming calls to a specific line or app without disconnecting the number. Callers usually go straight to voicemail or another team member instead of ringing through.
A missed call is an incoming call that ended without being answered. It may have rung out, been declined, or gone to voicemail. Most business phone systems flag it for a callback and log it separately from answered calls.
On-hold music is audio played to a caller while they wait to be connected, transferred or answered, replacing dead silence. It can be generic music, a custom recording, or messages about the business mixed in.
Visual voicemail shows a list of voicemail messages on screen, each with caller ID, timestamp and duration. Any message can be picked and played instantly. It replaces dialing into a voicemail system and listening in order.
Voicemail transcription converts a voicemail message into text automatically. It arrives by email or app notification within seconds of the call ending. It lets a team scan what a voicemail says without dialing in to listen.
Call recording laws set who must consent before a business call can be recorded. Rules range from one-party consent (only the recording business needs to agree) to all-party consent (everyone on the call must agree). These rules vary by US state and by country.
CNAM is the database lookup that turns a phone number into the name displayed on a recipient's caller ID. This could be a business name instead of just digits. It has to be registered and kept current for a business number.
E911 is the US system that automatically sends a caller's registered address to emergency dispatchers. This happens when they call 911 from a VoIP phone. Unlike a traditional landline, a VoIP number needs that address entered manually and kept current.
Know Your Customer is the identity verification process phone and messaging providers run before activating a business account. It typically checks a business registration, address and the identity of an owner or admin.
A robocall is a phone call placed by automated dialing software rather than a live person. It often plays a pre-recorded message. Unsolicited robocalls to consumers are heavily restricted under US and UK law. Legitimate businesses can still use automated calls for appointment reminders with consent.
Spam Likely is a carrier-generated label shown on a recipient's phone, warning that an incoming call is probably unwanted. It's based on call patterns, complaint history and caller ID authentication strength, rather than anything the business controls directly.
STIR/SHAKEN is a US caller ID authentication standard that lets phone carriers digitally sign calls. This proves the caller ID has not been spoofed. As of July 2026 it has been mandatory for major US voice providers since June 2021.
BYOD lets employees use their personal smartphone or laptop for business calls and texts through an app. The business doesn't issue separate work-only hardware. The business number stays separate from the person's personal number.
A desk phone is a physical handset sitting on an office desk. It connects to a business phone system over the internet (VoIP) rather than a traditional phone line. It works alongside or instead of a softphone app.
An extension is a short internal number, often 3 or 4 digits. It routes a call to a specific person or department within a business phone system, without needing a full external phone number for each one.
Presence shows a teammate's real-time availability, such as available, busy, on a call or offline, inside a phone system's app. Colleagues then know whether to call, message or wait before reaching out.
A softphone is an app that turns a computer or smartphone into a business phone line. It lets you make and receive calls over the internet instead of using a physical desk phone. It uses a headset or the device's built-in mic and speaker.
Call logging is the automatic recording of call details, such as timestamp, duration, participants and outcome, into a CRM or other business system. That way, no one has to manually type up notes after every call.
Click-to-call lets someone place a phone call by clicking a contact's number inside a CRM, website or app. This works instead of manually dialing digits on a phone. The call routes through the connected business phone system automatically.
CRM sync automatically logs calls, texts and voicemails from a phone system into a customer relationship management tool. It attaches them to the right contact without anyone typing notes manually after each call.
A screen pop automatically displays a caller's CRM record, past interactions or ticket history on screen the moment their call rings in, before anyone answers. That way, the team member already has context when they pick up.
A webhook is an automatic notification a phone system sends to another app the instant something happens, like a call ending or a text arriving. This lets that other app react immediately without checking back for updates.
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