COMMAND.COM is the default shell for Microsoft operating
systems, including MS-DOS and Windows versions up through Windows ME. Other
versions of DOS not from Microsoft also have a command shell named COMMAND.COM,
including DR DOS and FreeDOS. It allows users to execute commands and run
scripts known as batch files. It has been superseded in Windows NT and by
extension all modern versions of Windows by CMD.EXE and PowerShell.
Techopedia Explains COMMAND.COM
COMMAND.COM is the command shell on MS-DOS and PC-DOS, as well as versions of Windows that depend on DOS (Windows 1.0 to Windows 95, 98 and ME). COMMAND.COM gives users a command line interface to DOS as well as a way to run scripts called “batch files” with the .BAT file extension. COMMAND.COM reads the AUTOEXEC.BAT file to automatically run commands on startup. Most of these consist of setting environment variables and loading device drivers for the various hardware components installed in the computer.
COMMAND.COM has a very simple list of commands for manipulating files, such as DIR for listing directories or DEL for deleting files. As it can be used for writing scripts, it has some simple flow control commands such as IF statements.
COMMAND.COM has largely been superseded by CMD.EXE, which debuted in OS/2 and Windows NT. Since all the versions of Windows since XP have been based on NT, CMD.EXE is now the default shell when opening the Command Prompt in Windows.
To maintain compatibility, other DOS versions created by other developers, including DR DOS and FreeDOS, have a shell named COMMAND.COM as well.