Deferred Revenue
Deferred revenue is created when a client has paid for work that has not yet been completed. When the work is invoiced (T&M/NTE) or revenue recognition run (FP), the deferred revenue is consumed. Deferred revenue can also be transferred from one contract to another; this is most likely for prepayment and service credit scenarios.
In addition to the content here, there is also a Deferred Revenue Adjustment Report type.