Earlier quoted context omitted.
It's Steam's downstream fork of Wine, which is not an emulator.
1. An emulator is a system which implements another system's functionality so as to serve as a usable replacement. Examples include in-circuit emulators for hardware components, or software emulators for game system hardware. In each case, the emulator is a usable replacement for the original system. 2. WINE reimplements the functionality of Windows, as exposed by the Windows ABI, as software running on Linux. 3. The…
> Wine (originally an acronym for "Wine Is Not an Emulator") is a compatibility layer capable of running Windows applications on several POSIX-compliant operating systems, such as Linux, macOS, & BSD. Instead of simulating internal Windows logic like a virtual machine or emulator, Wine translates Windows API calls into POSIX calls on-the-fly, eliminating the performance and memory penalties of other methods and allowing you to cleanly integrate Windows applications into your desktop.
QED