Chromecast is a streaming device developed by Google that allows users to play content from their smartphones, tablets, or computers directly on their TVs. It connects to the TV's HDMI port and uses Wi-Fi to stream videos, music, and other media from various apps like YouTube, Netflix, and Spotify. To use Chromecast, users simply need to install the Google Home app on their mobile device, set up the device, and select the content they want to watch. The device acts as a bridge, enabling users to control playback from their mobile devices while enjoying a larger screen experience.