Web redirection lets you give out a Pobox web address that matches your Pobox lifetime email address. You can point your Pobox web address at any URL you like -- a blog, your Flickr photo stream, your website, whatever you want.
So, for your address you@pobox.com, the Pobox web direction address would be http://pobox.com/~you.
Additionally, Pobox also now supports URL Redirection for https — albeit, only for addresses hosted at @pobox.com domains; custom domains must still use the generic http.
Web redirection is not intended to obscure the URL of the actual website you are using. That is to say, when the page finishes loading, the person looking at the page will be able to see the URL of the page you directed it to, not your Pobox web address.
Additionally, all your Pobox addresses must be directed to the same web page. You cannot direct URLs by address.