Google Cast is a technology that enables multi-screen experiences and lets a user send and control content like video from a small computing device like a phone, tablet, or laptop to a large display device like a television.
The sender may be a phone or tablet running on Android or iOS, or it may be a laptop computer running Chrome OS, Mac OS, or Windows. A sender application running on the sender device uses the Google Cast API appropriate to its operating system to discover and transmit to the receiver application running on the receiver device. You can use the sender APIs to enable your Android, iOS, or Chrome app to send content to a large display.
The receiver device is optimized for video playback with a receiver application that receives data over Internet Protocol and transmits it to the television. The receiver API lets you customize the messaging between the sender and receiver applications for authentication and other scenarios.
While content is playing on a TV, a user can multitask on their device without interrupting the video playback. For example, a user can search for a video on their phone’s YouTube application and then send the video to their TV via a Google Cast device. The user can play, pause, seek, and control volume using their phone, they can search for other videos to watch, and even check their email while the content keeps playing on the TV.
See the Developer's Guide to get started building a Cast application.