We are playing the Pokémon Community Game!

During stream every 15 minutes a wild Pokémon appears in chat. You can use your pokeballs to attempt to catch it. The commands how to do that are listed below.

Inside the extension (linked above - or directly on Twitch in the panels) you can check out your Pokémon, your items and you also can fight other trainers in battles. The extension also displays the weekly quests in which you can get extra loot.

Until I was able to extend this page, you will find all infos about the game and its commands in the linked FAQs above