I am a new iPhone user and have an iPhone 4s . Can you please explain what AirPlay is and how can I get it? Also, please let me know some free links to download mp3 songs for my phone.
Apple explains AirPlay quite well at its official page, but I'll offer a brief summary:
AirPlay is a way to broadcast what's on your iOS device to other devices in your home. For example, let's say you're watching a movie on your iPad and decide it would look better on the big screen. Using AirPlay, you could push what you're seeing to your TV and enjoy it there. Note that AirPlay only works with devices that support it - any old TV won't necessarily be compatible. If you're interested in using this feature, I'd recommend buying an Apple TV. They're not terribly expensive.
AirPlay also lets you mirror your entire device's screen and broadcast it to a TV - great for showing off to a group or something of that nature. Certain games also allow you to use your iOS device as a "second screen" while the action takes place on your TV, perhaps a flight simulator game.
Finally, AirPlay lets you broadcast music to compatible speakers. This means you can start playing music in iTunes on your phone and use AirPlay to send it to your home speakers.
Once your iOS device and the Apple TV/speakers are connected to the same network, the AirPlay icon will appear automatically whenever the content you're using can be sent via AirPlay. It's fairly straightforward; try it out to see all that it can do.
I hope this summary helped you!
AirPlay is used to stream or display your media on other AirPlay capable devices.
You don't have to "get" AirPlay as it is already built into iOS on your iPhone.