Command lines help developers find certain stuff from their computer such as folders, pictures, music, videos programs, etc. by using a different interface than your normal Windows or IOS interface.
CLI was early used by computers to function and run software before our modern age interfaces. Also with CLI you can go deep into your computer and change or modify everything from scratch. Not many people know how to operate this type of processors which can be very difficult for the regular person who is more used to the stylish interface. Most of the time the CLI will be handle by professionals software developers when and update in the interface needs to be done,