CLI (Command-Line Interface)

Short for command line interface, CLI is a user interface common to MS-DOS computers. The user sees the command line on the monitor and a prompt that is waiting to accept instructions from the user. The user types in the command, the computer acts on that command and then issues a new prompt for the next instruction from the user.

CLI operating systems are becoming less used as GUI operating systems gain in popularity.

Source: https://www.webopedia.com/