Sometimes referred to as the command screen or a text interface, the command line or Windows command line 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 >. 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?
Because a command line interface requires unique commands for different operations, this interface is often more difficult to learn because of the need to memorize dozens of different commands. However, a command line operating system can be a very valuable resource and should not be ignored. For example, users who have Microsoft Windows may find a task such as renaming 100+ files in a folder, a very difficult task. However, renaming 100+ files in a directory can be done in less than a minute with a command entered into the command line.
The command line is still used even today because it is still easier for someone who is familiar with a command line to perform tasks that may be possible in a GUI but can be done faster in a CLI or automated using scripts.