Can you have a forum that is only visible to certain people you have selected in a group?

I have looked at permissions in categories and forums and it says groups but I don't know whether we can distinguish between certain groups, will they just appear if we make them so we can choose them?

If it possible I would like to find out how to do this?

Well, its possible to do that i think. Just create a group & give them permissions for that forum to view & reply to topics. For normal members, do not give them any permissions.
Users & groups>Group administration

General>Categories and forums
Permissions tab

that worked thank you.