The command line, also called the Windows command line, command screen, or text interface, is a user interface that is navigated by typing commands at prompts, instead of using the mouse. For example, the Windows folder in a Windows command line is "C:\Windows>" (as shown in the picture) and in Unix or Linux, it may be "%" or ">" depending on the shell. Unlike a GUI operating system, a command line only uses a keyboard to navigate by entering commands and does not utilize a mouse for navigating.
Why do people use the command line?
Although using a command line interface requires the memorization of dozens of different commands, it can be valuable resource and should not be ignored. Using a command line, you can perform almost all of the same tasks that can be done with a GUI. However, many tasks can be performed quicker and can be much easier to automate and do remotely.
For example, users who have Microsoft Windows may find a task such as renaming 100+ files in a folder, a very time intensive task. However, renaming 100+ files in a directory can be done in less than a minute with a single command in the command line. The task could also be automated using a batch file or other scripts to run instantly.