A p.o. address, for example, may tell you how to get to someone's apartment but it wouldn't tell you how to get up there if the front door is locked. A URL may

A p.o. address, for example, may tell you how to get to someone's apartment but it wouldn't tell you how to get up there if the front door is locked. A URL may tell you how to get to someone's file, but it wouldn't tell you how to download it if the server required authentication. A URL might be more comparable to driving directions than a mere address, but it does not grant access to a resource with even the most rudimentary access control.