CLI (Command Line Interface) is a man-machine interface in which the user interacts with a computer system by entering lines of textual instructions to ask the computer to perform operations, which are interpreted by a “Shell” (as opposed to the use of a graphical user interface, or GUI). 

Here is an example of the instruction lines of a CLI written in MySQL:

mysqldump -h host -u user
-ppass -rfile database [tables]