Bookings, billings and revenue
Bookings are the value of contracts signed, billings are what has been invoiced, and revenue is what has been earned by delivering the service. For a subscription business the three move on different timelines, so a signed multi-year deal can raise bookings today while revenue arrives gradually over its term.
How to read it
Confusing them is a common source of mismatched board and finance numbers. Decide which one each report uses, label it, and reconcile them through deferred revenue rather than forcing them to agree.