Compatibility layer

In simple terms, a compatibility layer is an interface that allows programs not written for a system to run on another system.

For example..Wine ( an acronym for "Wine Is Not an Emulator") is a 'compatibility layer' capable of running Windows programs on several operating systems, such as Gnu+Linux, macOS, & BSD. You can use Wine alone to run Windows programs, but it requires a fair amount of technical expertise. With Proton, CrossOver, Lutris, and play on Linux, you don't need to be an expert.

Lutris

Wine is the main part of what makes up Lutris and enables a bunch of games to work. Lutris offers community scripts that automatically configure the Wine environment. Lutris also offers integration for software purchased from GOG, Humble Bundle, Steam, and Epic Games Store; those can be launched directly through the Lutris application.

CrossOver

CrossOver is a proprietary program based on wine. it is available for Gnu+Linux, macOS, and Chrome OS. CodeWeavers modifies the Wine source code, applies compatibility patches, adds configuration tools that are more user-friendly, automated installation scripts, and provides technical support.

PlayonLinux

PlayonLinux is a fully graphical interface to use Wine, free and easy to install, that allows you to install Windows games on Linux. In other words, all the complexity of Wine is hidden by default in PlayOnLinux and easily automates the installation of compatible software and games. Installing Windows applications with those programs are crazy  simple. You just pick, which popular Windows app you want to install and either start the download or pop in the CD or DVD.

Proton

Proton is a compatibility layer for use with the Steam client which allows games which are exclusive to Windows to run on the a Gnu/Linux device. It enables users to install and run Windows games that do not offer native Linux versions. Proton is developed with cooperation between developers at Valve and CodeWeavers.

Conclusion...

Compatibility layers are a must have application for the people migrating from Windows to Linux operating system. But be aware So, a compatibility layer like wine can only be a helper. If you need to play every single piece of Windows  to just work, Gnu+Linux is the wrong platform for you.