Never heard of that .. please explain
It's a peer to peer(p2p) file sharing system. Remember Napster or Limewire? It's like them except way way way faster.
There's damn near any movie you can think of available. It's "illegal" since most of this stuff is licensed to large studios but no user has ever been arrested because of it.
To make it work you need a computer, an internet connection and a client. The client is a piece of software that interfaces with the bittorrent network for you. Common ones are uTorrent, Deluge and Transmission. There are literally hundreds of others but uTorrent is by far the biggest and it's well documented.
Once you have a client you simply go online to a torrent site. Search for what you want and download the torrent hash file. Each upload gets it's own unique hash number. It can only be generated once and is specific to that torrent. You click on that download and your torrent client opens. Then you just wait for the files to be uploaded to your comp.
It's a little more complex than what I just wrote but if you want to read some guides for it just google bittorrent. I've been using it for 15 years now. It blows streaming services out of the water.