Unlike Miracast and DLNA, AirPlay is proprietary and not an open standard, which means Apple gets to control who uses it.
AirPlay is to share everything including music and movies to apps and games from your iPhone, iPod touch, and iPad to your Apple TV
AirPlay is Apple's term for their audio and video streaming technology. It's what lets your iOS 5 device, or iTunes on Mac or Windows, beam videos over Wi-Fi to your Apple TV so you can watch movies and play games on your big screen TV, or music to your AirPort Express router, so you can listen on your higher quality speakers.
AirPlay Mirroring is a recent addition to iOS that works with iPad 2 or iPhone 4S and above to let you not only beam music or video, but entire iPhone or iPad apps. Anything from Facebook to your favorite crosswords, racing, or fighting game can be sent via Apple TV to your HDTV, with your iPhone, iPod touch, or iPad remaining active as the controller.