So, you get entrance to your Xbox Gamertag, achievements (many of which are available in Windows games), and even the ability to stream games from your Xbox to Windows.
It’s available besides the Xbox Console Companion as a way to bring console-like gaming to Windows.
The Xbox Game Bar in Windows 10 is part of the Xbox gaming activity on Microsoft’s desktop OS. Hit the Windows + G key to open the Xbox Game Bar on the desktop over your game.