Because the alternative is a CSV. It is exported on Monday, edited on Tuesday, sent to three people on Wednesday, and by Friday four of its accounts have churned and two have doubled.
A segment is a saved query over contacts or companies. It is evaluated when it is read, so its membership reflects the records as they are now rather than as they were when it was built.
You build a segment from any field on the record, including enriched values, deal state and support standing. It has a name and an owner, and anything that can act on a list can point at it.
"Renewals in the next 90 days with an open escalation" is a segment, not a spreadsheet. It was 14 accounts in January and 6 in March without anybody rebuilding it, and Desk changed both numbers.
It is not a static audience. If you need the exact membership as it stood on a date — for a mailing record or an audit — take a snapshot, which is a deliberate and separate act.
Growth targets campaigns at them, sequences enrol from them, routing rules can reference them, and reporting can group by segment membership over time.
Yes. Support standing from Desk and payment state from Books are on the same record, so they are queryable.
They are evaluated against indexed fields. Very large segments used constantly can be materialised on a schedule.
Only if you share it with edit rights. Shared read is the common case.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.