There are many reasons may make you to seek to display your iPhone, iPad or iPod touch content on a big screen.
With AirPlay Mirroring you can mirror exactly what’s on your iPhone or iPad to your HDTV over to an Apple TV or a compatible AirPlay receiver app on a Mac or PC like Reflector or XBMC, including the audio stream if one is avialable.
You can through Airplay Mirroring feature watching video on a larger screen, web browsing, gaming on a bigger display, teach or demonstrate iOS apps or anything of your interest, look at picture slideshows, and so much more.
AirPlay Mirroring Requirements
In case you would used the feature with Apple TV:
iPhone 4 or later, iPad 2 or later, iPod touch (5 generation) Apple TV (2nd or 3rd generation.)
Both the iOS device and you Apple TV must be on the same wi-fi network.
How to Use AirPlay Mirroring in iPhone or iPad
Swipe up from the bottom of your iOS device screen to bring up Control Center, then tap AirPlay icon.
Tap the name of the Apple TV, then toggle “Mirroring” to ON.
Once the AirPlay Mirroring is enabled, your iOS device screen will be mirrored on your Apple TV.
If “AirPlay” icon is not visible in Control Center be sure that the Apple TV is online and active. You can enable or disable AirPlay on Apple TV in the AirPlay menu: Settings > AirPlay.
One other common problem is if you find only the audio is streaming over without the screen display showing up on the Apple TV, you are probably simply forgot to toggle the “Mirroring” option ON from the Control Center, so enable it as described above.
How to turning Off AirPlay Mirroring in your iPhone or iPad
AirPlay will stay on until you turn it off, to do that from Control Center again, tap on the ‘AirPlay’ button.
Select the device name from the list, and tap "Done" to prevent both the AirPLay and the mirrored stream instantly.
If you just switched the "Mirror"option to off, the display will turn off while keeping the AirPlay audio stream active, so you will want to tap onto the device name to turn off the entire feature.
AirPlay in iOS 8
AirPay became more easy in iOS 8, that through new iOS 8 peer-to-peer AirPlay feature. You can now stream your iPhone (iPad, iPod) content to Apple TV without the need for a shared network connection, so it became far easier for people to use AirPlay in classrooms and businesses that may have complicated networks.
With iOS 8, you can wirelessly connect iPad, iPhone, or iPod touch to Apple TV without first connecting to the organization's network. Which means you can present or share your work even if you're offline or the organization has a complex network.
AirPlay with AirPort Express and third parity apps
Generally AirPlay feature used to stream video, music, and photos wirelessly to Apple TV and other AirPlay-enabled devices, you can use the feature (without Mirroring) in case you want just to stream the music, that through the AirPort Express device, or Airplay-enabled speakers or receivers.
As mentioned above you can also use Airplay mirroring with third parity apps that run in OS X, Linux, or Windows, like the Reflector, or XBMC to stream your iOS device content to your PC With the possibility of recording this content.
Capture your iPhone or iPad screen in iOS 8 by a Mac
You can now in iOS 8 capture an iOS device screen-content without a third party app. If you plugged an iOS 8 device into a Mac via USB will show up as a camera, which can have its screen be recorded in QuickTime.
We would also pointed out that you can connect iPhone to a TV, projector, or other external display using the appropriate Apple cable or adapter, like the Lightning to Digital AV Adapter or the Lightning to VGA Adapter.
All points on iOS 8 are updated.