Microsoft started taking sign-ups for its Project xCloud game streaming service about three weeks ago, and it started sending out invitations to test it earlier this week. While the original plan was to start with a small group of testers, the company says that community feedback has been so overwhelming that it's sending out more invites today.
At this time, Project xCloud requires that you use an Android device, running Android 6.0 or higher. It will be coming to other platforms though; in fact, the goal is to be able to play your games from any device.
Once you get your invitation for xCloud, you'll be able to play Gears 5, Halo 5: Guardians, Sea of Thieves, and Killer Instinct. While you're testing it out, all of the games should be free.
The other half of Project xCloud is that you'll soon be able to stream games from your home console, rather than only from the cloud. This isn't available just yet, but it should be coming to Insiders soon. But if you've signed up for the Project xCloud preview, Microsoft says you should keep a close eye on your inbox.