AirPlay allows users to stream audio and video content online or stored in devices to AppleTV and connected entertainment systems through a wireless connection. Media sharing works similarly to accessing an unprotected media file shared across a network.
AirPlay makes it possible to use iOS-based devices as presentation tools through mirroring mode. In dual screen mode, AirPlay can enable iOS as a flexible touch screen controller, with motion sensing and communications enabled. That capacity is significant for gaming applications.
Apple lists the following requirements for AirPlay support: Apple TV (2nd generation or later) with an iOS device running iOS 4.3 or later or a Mac with iTunes 10.2 or later.
Some features require relatively current software:
Peer-to-peer AirPlay requires a Mac (2012 or later) with OS X Yosemite or an iOS device (late 2012 or later) with iOS 8; and an Apple TV (3rd generation rev A, model A1469 or later) with Apple TV software 7.0 or later.
Mirroring is available with iPhone 4s or later; iPad 2 or later; iPad mini; iPod touch (5th generation); and iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), MacBook Pro (Early 2011 or newer) and Mac Pro (late 2013) with OS X Mountain Lion or later.
Dual-screen capability is available with iPhone 4s or later, iPad 2 or later, iPad mini and iPod touch (5th generation).
See a video tutorial on setting up AirPlay to connect a Mac to Apple TV: