One identity, several endpoints
A line can ring a desk phone and a browser at once, and a transfer to that extension does not need to know which one the person is using today.
An extension belongs to a person, not to a desk. Someone working from home, from a client site, or from a laptop in an airport is reachable on the same number and shows the same caller ID going out.
What the call does
A line can ring a desk phone and a browser at once, and a transfer to that extension does not need to know which one the person is using today.
Every line that can dial out carries a registered service address. When a line turns up on a network it has not used before, we ask the person to confirm where they are sitting rather than assuming the office.
Weather, a power cut, a burst pipe. The call flow does not care. Pointing a number at a group of browsers instead of a group of desks is a change you make yourself, in minutes, from anywhere with a connection.
Most people never open the second column. It is one click away rather than spread across the first.
On every plan
This is included whichever plan you are on, with no add-on and no module to enable. Plans differ by how calls are distributed and how long the history is kept.