Twitch is an online website that allows users and gamers to watch or stream their game play. The videos can be live or pre-recorded. Twitch also hosts tournaments between competitive players.
To watch Twitch a broadband connection over 5Mbps will work fine. If you plan to stream on Twitch, an upload speed of 5Mbps will allow to stream HD Video (720p or 1080p). To streak 4K quality video you will be looking at a minimum upload speed of 25Mbps.