Kay - this site (following) will explain the premium membership for Ancestry.com. I have had this subscription for 2 years now and have yet to pay for anything "extra". Your annual subscription fee pays for anything and everything you are able to access on Ancestry. I would suggest that anyone doing any family research should ONLY subscribe to the World (premium) subscription otherwise you are wasting your money.
www.ancestry.co.uk/subscribe/products/default.aspx?p=uk_premium.