What is Unix command?

A command is an instruction to the computer, which it interprets to perform a specific task. Most commonly a command is a directive to the command-line interface such as Shell.

What is CMD in Linux?

The Linux command is a utility of the Linux operating system. All basic and advanced tasks can be done by executing commands. The commands are executed on the Linux terminal. The terminal is a command-line interface to interact with the system, which is similar to the command prompt in the Windows OS.