For those unfamiliar, Steam Play is where users only need to make a single purchase of a game to enjoy it on their Mac, Windows, or Linux computers, assuming that the game in questions supports those platforms. However with the improved version of Steam Play, it will now allow games created for Windows to run on Linux, even if the game does not have a native Linux version available.
According to Valve, this also means complete native support for Steamworks and OpenVR, and that DirectX 11 and 12 implementations will be based on Vulkan. There is also improvements made to fullscreen support, game controller support, and more. Essentially Linux gamers will be able to enjoy Windows-based games without feeling like they are getting a poor quality port.
That being said, not all games are supported just yet, and note that this version of Steam Play is still in beta which means that certain quirks and bugs probably still need to be ironed out. In the meantime gamers who are interested can head on over to the Steam Community page to check out the list of games that are currently compatible.