Came across the term for the first time when I was checking out stuff on the play Store. It’s another project by Google, which in itself is naught but like a USB flash drive, but there’s more to it.
The Chromecast enables you to enjoy media content on your HDTV. Means if for example you come across a YouTube Video, while checking out your Facebook feeds, all you have to do is look for and press the chromecast button. It would prompt you with a list of available devices, selecting any of which would play the content on whatever device you chose. To do so, what you are gonna need is true chromecast USB device of course which has to be plugged into the TV.
Here, a link to the official video: