despite the funny backronym, Wine actually IS a WINdows Emulator. Someone apparently told them that it's only called an emulator if it's emulating a CPU architecture, but that's not true.
If you squint a bit (well, a lot really), Win32S on 3.1 and Windows 95’s Win32 implementation are Windows NT emulators running on top of 16 bit Windows.
“Emulator” is a term of art in this area which refers to emulation of a hardware (and usually machine instruction) environment. Ironically, “translation” (as in instruction translation), as proposed by a sibling comment, is an even more connoted-with-hardware-emulation term.
WINE is … well, most directly it’s just an implementation of an API (the Windows APIs). In webdev parlance it might be called a “polyfill”. Perhaps a “compatibility shim”?
I think in common usage, people expect an "emulator" to be a more sandboxed translation layer than Wine, for example, provides.
e.g. it's probably a security vuln if loading a Game Boy ROM reads arbitrary paths on your local filesystem determined by the ROM's code, not so much with Wine.
Someone made a cute demonstration that I think usefully encapsulates this a while ago. [1]
Mostly because the Gameboy doesn't have any IO register to reformat your hard disk. If the emulator interpreted some instruction as reformatting your hard disk, that would be a bug because it's not interpreting it as whatever it actually does on a real Gameboy.
For me an emulator works to simulate the hardware which is very different from translating API calls. THe result may appear to be same, but the approach is very different.
They don't. They use WINE, which as the name says, Is Not an Emulator. :D
(I'll let my pedantic self out now)