Web and Ranking

Looking for clarification on the need for Ranking when accessing ticket inventory - there seems to be some info missing and/or I'm having a brain freeze. We are told that a constituent must have a Ranking to access ticket inventory via the web. Access to inventory sounds like access to tickets on sale. Since only "known" constituents can have a chance of having a ranking how would the General Public be able to access tickets is rank was required? From reading the documentation - ranking is needed on the web ONLY for pre-sale or a limited access period. Otherwise Ranking is just a criteria like Constituency or List and used in Price Rules -- right?