The Facebook build target lets you deploy your projects to either the new Facebook Gameroom desktop app for Windows as a native Windows player, or to Facebook.com using Unity’s WebGL support. With Gameroom, Facebook is introducing an easier way for developers to bring high-quality games to the PC to take full advantage of the CPU and GPU native power.
When the Facebook target build is active in the Unity Editor, you can use the Facebook SDK for Unity API to share content with Facebook friends, access the Graph API, and more. You will also be able to use the Unity IAP service to handle in-app purchases on Facebook. Everything you need comes integrated with Unity out of the box — you can even upload your builds to be hosted by Facebook directly from the Unity Editor.