Wine

Wine Is Not an Emulator — a translation layer that reimplements the
Win32/Windows API on POSIX systems, so Windows programs run natively on
Linux without a VM or Windows license.

Key concepts:

• Prefix — a virtual C: drive (registry, system files, app data).
  Each prefix is isolated; create one per app to avoid dependency clashes.
  Bottles calls managed prefixes “bottles”.
• Runners — versioned Wine builds you swap per prefix.
• winetricks — helper to install common redistributables into a prefix.

Wine translates API calls; it does not emulate CPU instructions (that’s
why “not an emulator” — x86 Windows apps run as native x86 Linux
processes).

Proton is Valve’s Wine-based gaming stack; UMU runs Proton outside
Steam.