Some commands can be entered simply by typing one word. It is also possible to combine commands so that the output from one command becomes the input for another command.
Combining commands so that the output from one command becomes the input for another command is known as piping.
Flags further define the actions of commands. A flag is a modifier used with the command name on the command line, usually preceded by a dash.
Commands can also be grouped together and stored in a file. These files are known as shell procedures or shell scripts. Instead of executing the commands individually, you execute the file that contains the commands.
To enter a command, type the command name at the prompt, and press Enter.