Command Line Interface / CLI
A command line interface or CLI is a way for humans to interact with a computer or other device without any graphics. It is often considered the opposite of a graphic user interface. A CLI consists of a terminal where text commands can be typed at a prompt to do different actions.
Most consider the CLI to be far more powerful than any GUI because of the number of things that can be done in one or two commands.
Most CLIs are actually driven by scripting languages, such as Bash, that allow direct coding of different actions or the creation of functions that are available as commands that are available any time you use the CLI. Every time you use a CLI you are literally writing individual lines of code telling the computer what to do in that moment.