What is Twitch?
Twitch [twitch.tv] is a website where you can watch and publish live streams for free. Live streams are videos of something that is being recorded as you watch it.
Twitch is famous for its game-related livestreams—which it provides direct support for by categorizing streams by game, and prominently displaying popularly streamed games (as of writing: League of Legends, Counter-Strike, Grand Theft Auto V, VALORANT, Call of Duty: Warzone, Dota 2, Path of Exile 2, and Fortnite).
Twitch also hosts live streams of other genres, such as art live streams showing artists drawing, DJ's live streaming music, and IRL live streams of events occurring outside a computer such as chess matches.
Quotes
Observation: for some reason Twitch's website never asserts that it's free to stream on it, so I can't quote them on that. I'd have hoped this to be on their about page [https://www.twitch.tv/p/en/about/] (accessed 2025-04-10), but no information at all can be found there.
Is Twitch Broadcasting Free?
Yes, it is free. You can also watch content on the platform at no extra cost.
https://streamyard.com/blog/how-to-stream-on-twitch (accessed 2025-04-10)