A shell is any user interface, whether command-line or graphical, that allows users to interact with the operating system to access services, features, and applications.
- In Unix (Linux and macOS), the word “shell” almost exclusively refers to a command-line interface.
- In Windows, the term “shell” can describe the graphical user interface (GUI) that includes the Start menu, taskbar, desktop, and File Explorer, i.e. the Windows shell. It can also refer to a command-line interface like PowerShell.