CLI
A command-line interface or command language interpreter (CLI), also known as command-line user interface, console user interface, and character user interface (CUI), is a means of interacting with a computer program where the user (or client) issues commands to the program in the form of successive lines of text (command lines).[2]
Command line
The command line interface, as opposed to a graphical user interface (GUI) is less abstract. The command line interface is sparse, not very visual, but "more true" in my opinion. I prefer the command line because it removes one layer of abstraction from my work.
Please click here for an excellent "cheat sheet" for command line [3]. For an interactive version of the same document please click here