Shell

The shell is a computer program that essentially allows users or other programs to access the tools and services of an operating system. Generally, operating system shells use a command-line interface or GUI. A broadly popular tool is Bash (UNIX/Linux).

CLI-based shells will give us a prompt, where we can then input commands.

zha:~$
zha:~$ echo hello
hello

The shell is in fact a programming environment, so we can do some more complicated things.