Tecmint: There are thousands of tools, utilities, and programs that come pre-installed on a Linux system. You can run them from a terminal window or virtual console as commands via a shell such as Bash.
A command is typically the pathname (eg. /usr/bin/top) or basename (e.g top) of a program including arguments passed to it. However, there is a common misconception among Linux users that a command is the actual program or tool.