TWITCH AFFILIATES is a program whereby appointed game broadcasters can earn royalties through monetisation and streaming tools. Starting today, though, additional revenue can be made through sales of games and items on gamer channels.
The tool that made this initially possible was called 'Cheering With Bits' which gave gamers the ability to earn royalties for the time spent streaming games on their Twitch channels.
If gamers host games and in-game items on their channels and manage to obtain sales, they can get as much as a 5% cut of the sales. All current Affiliates have already automatically had their Twitch channels upgraded with this option. If they are playing a game that's available to buy on Twitch, then the purchase button will simply appear on their channel for that game.
If you wish to learn more about the Affiliate program, you can read more about it on the Twitch Help site.