What worth is FreeDOS?

Some manufacturers are selling computer with FreeDOS operating system. I am curious what worth this FreeDOS is. Do I have to buy Windows Visa separately and install?

I would like to know what I can do with FreeDOS.

I see little benefit it is an old command line Operating System which you can do some very limited things with outside of your main OS, but still need an OS like Windows XP/Vista or even Linux.

See http://en.wikipedia.org/wiki/FreeDOS for more information.