Google Chromecast is a streaming device that allows users to play content from their smartphones, tablets, or computers directly on their TV. It connects to the HDMI port of the television and uses Wi-Fi to receive and display videos, music, and other media from various apps like YouTube, Netflix, and Spotify. To use Chromecast, you simply need to install the Google Home app on your mobile device, set up the device, and select the content you want to cast. This makes it easy to enjoy your favorite shows and movies on a larger screen without needing a separate remote control.