awesome_pants
Banned
It might not be entirely sold out. It might vary venue to venue, but I know a lot of venues don't have all the seats up for sale during the pre-sale, just a selection of them.
Presale tickets are a batch of limited quantity tickets / certain sections of the venue. Typically venues allocate certain number of tickets to presale and have the remainder for general/public sale when that goes live. Presales may be sold out but a large portion of the venue will be available when tickets go public.