Wireless Mirroring/Casting displays via Wifi-direct (tech for both work/play) also called as WiDi

Wi-Fi CERTIFIED Miracast™ is a groundbreaking solution for seamlessly displaying multimedia between devices, without cables or a network connection. Miracast makes it easy to display applications or video content or images from one Wi-Fi device on another, even when the devices are different brands. Miracast connections are formed using Wi-Fi CERTIFIED Wi-Fi Direct®

Wi-Fi Direct Connections for Miracast are easy to set up and use since the devices choose the appropriate settings automatically. 

Wi-Fi Direct allows devices to connect directly to each other, without the need for a Wi-Fi AP, and requiring just the push of a button, the entry of a PIN, or tapping two NFC-capable devices together. Wi-Fi Direct allows source and display devices to discover one another and provides the underlying device-to-device connectivity for Miracast. Miracast builds upon Wi-Fi Direct with mechanisms to negotiate video capabilities, setup content protection (if needed), stream content, and maintain the video session.

The Main difference between Miracast and Wi-Fi Display is, Miracast is the brand for the certification program operated by Wi-Fi Alliance. Devices that pass this certification testing can be referred to as “Miracast devices”. Miracast certification is based on the Wi-Fi Alliance Wi-Fi Display Specification. This is the underlying technological specification developed by Wi-Fi Alliance members, and is copyrighted and owned by Wi-Fi Alliance.All Wi-Fi CERTIFIED products are tested for the latest generation of Wi-Fi security: WPA2 (Wi-Fi Protected Access 2). 

A most common use of it is to "share Android screen(Portable smaller screen) onto Tv(Larger screen)"

i.e We can see our video clips or photos without using cables, or we can play any game by mirroring the picture on the phone onto the screen of our TV.

To activate it in the mobile device we need to choose option like Screen Mirroring / Miracast/Wi-Di, where we need to select the TV as pairing device,  In a couple of seconds  we can see the display of small screen been displayed on  the TV.

If we don’t own a compatible TV we can purchase a Wifi disply adaptor, to get the same output.

Reference:-  http://thegadgetpill.com/share-android-screen-tv-smart-tv/#.V-vRSfl96M8