Raiding someone on Twitch is a great way to support fellow streamers. It's essentially a way to bring all of your viewers to someone else's live stream at the end of yours.
It not only acts as a great way to introduce your community to someone elses, but it's also a great way to boost the concurrent views of the person you're raiding. Plus, if they're a friend of yours – maybe they'll return the favor some day!
To start a raid, all you have to do is enter "/raid [username]" in your chat. For example if you want to raid Nickmercs, you would type "/raid Nickmercs".
When you've done that, you'll get a new prompt with a countdown timer to press a button that lets you run the raid instantly. When the raid begins, you and all of your viewers will be sent over to the person you're raiding.
Now what happens on the side of the person being raided? Well, they get a notification letting them know they're being raided. The notification also shows them of how many viewers the raider is bringing.
And that's about it! It's a really simple mechanism to collaborate with other streamers, show the love, and introduce your community to a new streamer friend of yours.