[stormbrew]

They're not really related concepts. A jail is allows you to run arbitrary things in a restricted environment while ssh's command feature just forces a particular command to run no matter what's passed.

If your authorized_keys line for a key has command="blah" on it and you go:

    ssh server ls

the server will, rather than running ls as it normally would, run blah and pass the command you specified in as an environment variable. Then blah can parse it and do whatever it wants with it.

You could use command to establish a jail or virtual environment of some sort in which to run the program specified if you wanted to.