Some have native Linux versions, while the rest can be "translated" (not strictly emulation, but the concept is close enough) via Proton, a translation layer that Valve introduced with the Steam Deck, which is itself running (arch btw) Linux. I'm not sure what the split is in the catalog, but the steam deck verified list serves as an indication for Linux (for Arch, at least) compatibility in general.

This is true for both Steam and non-Steam games - the developer or publisher might offer a native Linux version, but packaging is always a mixed bag. This proton trick allows you to run the Windows version with the same compatibility it would have on the steam deck, no matter where it came from.