What is an external command in command prompt in Windows?

An external command is a command which is not defined in the command.com. An external command makes use of external executable or com files to execute and by default only internal commands work directly in windows.

To use an external command you will have to specify the executable command executable or the com file with the required parameters. If you run commands which are not recognized in windows then you will get the error message that the command is not recognized as an external and internal command.