The shell provides the user a way to interact with the OS. It’s called shell, because it’s the outermost layer of the OS. There are two types: “Command-line interface” (CLI) and “Graphical user interface” (GUI).
User <-- Shell (CLI/GUI) --> OS
CLIs
Unix
- sh (Bourne shell)
- bash (Bourne-again shell)
- ash (Almquist shell)
- dash (Debian Almquist shell)
Windows
- cmd (Command prompt)
- pwsh (PowerShell)