Q: airplay

About AirPlay and Airplay Mirroring

AirPlay Mirroring requires a second-generation Apple TV or later, and is supported on the following Mac models: iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), and MacBook Pro (Early 2011 or newer). For non-qualifying Macs you can try using Air Parrot.

Several Apple Articles Regarding AirPlay

Apple TV (2nd and 3rd gen)- How to use AirPlay Mirroring

How to set up and configure AirPort Express for AirPlay and iTunes

About AirPlay Mirroring in OS X Mountain Lion

iTunes 10- About playing music with AirPlay

Troubleshooting AirPlay and AirPlay Mirroring

Using AirPlay

AirPlay is also used in some speaker and stereo system to send audio over a WiFI network. The Apple TV supports audio and video streaming. iOS devices can only send audio to one speaker.

When used with iTunes on a computer you can send audio to multiple devices at the same time for a whole home audio system. This setup can can be quite handy when controlled on an iOS device using Apple's free Remote app.