Use this tag for questions relating to Windows Subsystem for Linux, the compatibility layer developed by Canonical and Microsoft to run Ubuntu programs natively in newer versions of Windows.
WSL (Windows Subsystem for Linux), was introduced in Windows 10 (64-bit). It provides a Linux-compatible kernel interface written by Microsoft with no Linux code, so that a user-mode Ubuntu image can run natively on top, rather than in a container or virtual machine. This allows for resource-efficient access to bash shells and other Ubuntu programs within a Windows OS. Canonical partnered with Microsoft to develop WSL.
WSL is also known as bash-on-windows