A command line interpreter is a program that allows you to enter commands and then executes those commands to the operating system. It is literally an interpreter of commands.
Why do command lines still exist?
Unlike a program with a graphical user interface (GUI), such as buttons and menus operated with a mouse, a command line interpreter accepts lines of text from a keyboard as commands and then translates those commands into functions that the operating system understands.
If a computer can be controlled via easy-to-use applications with a graphical interface, you might wonder why anyone would want to enter commands via the command line instead. There are three main reasons.
The first is that you can automate the commands. I could give many examples, but one of them is a script to always close certain services or programs when the user first logs in. Another could be used to copy files of a similar size from a folder so that you don't have to dig through them yourself. These things can be done quickly and automatically using commands.
