The description below is from the book DOS the Easy Way by Everett Murdock Ph.D.
CLICK HERE for information about downloading the book.
Type: Internal (2.0 and later)
Purpose: Exits a secondary command processor.
This command can be used when you are running an application program and want to start the DOS command processor, then return to your program. For example, to look at a directory on drive B while running an application program, you must start the command
processor by typing COMMAND in response to the default drive prompt.
You can now type the DIR command and DOS will display the directory for the default disk. When you type EXIT, you return to the previous level (your application program).
If you start a new command processor by entering
then you can return to the previous command processor by entering