[timdorr]

Yes, the Quest 1/2 and Rift S do "inside out" tracking. They have 4 cameras (5 on the Rift S) on each corner of the front face plate that tracks the headset and controller positions in 3D space (in addition to internal accelerometers and gyroscopes).

This is, for the most part, what enables the Quest to be fully wireless. Because there is no base station or fixed position camera, you're not limited to where you can use it, nor how big your play area can be. If you're in a new space, you just draw a guardian border around your play area and you're good to go.

The "passthru" feature mentioned above lets you see the camera feeds composited together in the headset display. It's very helpful for things like moving a chair out of the way or finding your controllers if you put on the headset without grabbing them. This new API allows developers access to this camera feed and to interact with its display for AR applications.