Regard PatBot as a very special Internetbrowser. Patbot visits the same websites (= server) with free patents, which you can visit with your web browser.
However, PatBot does this automatically. You enter the patent number. PatBot visits the servers known to provide this kind of patents and tries to download the patent. If the requestet patent can't be found, PatBot reties the next item of it's server list. If ordered, PatBot offers a list of corresponding patents.