The Steam Play program – once you buy the game, you immediately get versions for Windows, Mac, and Linux, if they are on the Valve platform. Today, Steam Play has expanded: now the program allows you to run on Linux, even those games that were not originally on Linux.
Just note that it’s really not a miracle to wait: for Steam Play on Linux Valve uses Proton – a modified version of Wine. This is a popular compatibility tool that helps to play Linux on games written for Windows.
By default Steam on Linux runs through Proton those games that are in the “white list”. Valve checked these games personally and made sure that everything is in order with compatibility. However, users offer additional options: to include Proton in general for all games in the Steam catalog or to install an alternative compatibility tool.
Proton has completely open sources, anyone can search through them. On Steam it is allowed to implement the custom Proton assembly and run games through it.
As noted by Valve, the best way through Proton is those games that use the graphics API Vulkan. With this condition, the performance on Linux should not decrease at all. But if the developers build a tricky DRM or a complex system of anti-cheats, then the game can not run through Proton at all.