What is the difference between Airplay and Bluetooth?

Airplay uses an existing WiFi network to stream audio and/or video from a compatible iDevice to a single Airplay enabled audio or audio/video receiver, or from iTunes to multiple audio or audio/video receivers, with individual volume control capability on each of the multiple units. Since WiFi has a large bandwidth, there is no compression of the streaming media using Airplay, so there is no degradation of quality. Bluetooth can stream only audio in a compressed format over a low-frequency, non-WiFi signal to one individual device at a time.