A command-line interpreter or command-line processor uses a command-line interface to receive commands from a user in the form of lines of text. This allows for a very basic user interface to set configurations, invoke executables and providing information to them as to what actions they are to perform on an operating system. For brevity, command-line interfaces are abbreviated here as CLI. Usually command-line interfaces are a textual component to an OS's shell.
Terminals are a common way to refer to CLIs and were once the preferred way of interacting with a computer. Today the word, terminal, often gets used when referring to a terminal emulator. Terminal emulators, are actually a software program that emulates hardware terminals of old. Now terminals are normally just applications that give a CLI to an operating system's shell.
One of the most common ways to use a CLI is to both navigate and manage files. There are a few common commands that nearly always gets used to do this.
ls - List files in the current directory.cd - Change directory.mkdir - Make directory.rm - Remove file or directory.mv - Move file or directory.cp - Copy file or directory.touch - Create a new file.cat - Catenate files and print on the standard output.These are all part of the GNU CoreUtil suite of tools.