See the Interactive Television Institute.
Headend - (a.k.a. Head-end, Head End. Cable Plant, Cable Transmission Center) - A headend was primarily used as a cable TV term in the past but now also might be used to describe a telco TV provider's local transmission facility. The headend is the physical location in your area where the television signal is received by the network operator, stored, processed and transmitted to their local customers (subscribers.) It has final control of the broadcasted content. In terms of interactive television, the headend can be responsible for ensuring the quality of interactive features as well as inserting ads and video on demand.
convergedigest.com/bp-ttp/bp1.asp?ID=61&ctgy=headendHead-end-based Personal Video Recording