User's Sync - Now How Doe New Users Registration Work?

Ok, I synced the users between this site and one of our subsites.

Master - http://www.powwows.com
Sub - calendar.powwows.com

I'm trying to figure out how this will work now.

So if someone goes to calendar.powwows.com and registers, will that sync back with PowWows.com?

And will it go the other way?

Or do I have redirect registration to the main site?

Thanks