Wine is a Windows compatibility layer that lets you run Microsoft Windows applications and games on Linux, macOS, and Android (experimental). No code emulation or virtualization occurs when running a Windows application under Wine, thus the name (Wine Is Not An Emulator).
You can use Wine as a stand-alone app to directly launch Microsoft Windows applications and games, or via a third-party tool such as Lutris on Linux. Wine is also used by Proton, Valve's Steam Play compatibility layer that allows playing Windows games on Linux, and by CrossOver, a commercial Microsoft Windows compatibility layer for macOS and Linux, among others.
I keep seeing Ubuntu (and Ubuntu-based Linux distributions like Linux Mint or Pop!_OS) and Debian 10 users trying to install Wine and running into dependency issues, so I thought I'd make a post about properly installing Wine Staging and Development builds (and Stable, though there are no dependency issues with these builds).