Yep. A private thread is like a "private chatroom" where only the selected participants have access to the data. If you wish it to be one-on-one, you just make it a point to only select one member.
---- The day Microsoft makes a product that doesn't suck is the day they make a vacuum cleaner.
I see that this has been asked before but I'm bringing it up again. While the private threads are nice, they do not serve the same function as a mail system. To begin with, most PM systems notify you when you have mail. As far as I can tell, you do not have any sort of popup warning when you have a response in your private thread nor a link that takes you directly to it.
Even if there was a notification, private threads are simply not the same as mail. We are moving our guild here from another site and private threads are the "feature" I've had the most difficult time explaining. People are use to being able to PM other members, get a response and get a popup or flashing message when they have new mail. It really is a feature that needs to be added.
BTW, I see that there have been several different threads requesting this over the past few years...