We support any headset that uses SteamVR including HTC Vive, HTC Vive Pro, Valve Index, Windows Mixed Reality HMDs*, and Oculus Rift.* The Index and Vive lines use SteamVR as standard. The Oculus and Windows Mixed Reality headsets don't use it as standard but can be run through SteamVR. Also, it should be noted that SteamVR is the program that allows the computer to launch and run VR experiences whereas Steam is a marketplace.
*must be running SteamVR content