A doorway page is a web page that is packed with high-volume keywords and anchor text in an attempt to trick the search engines into ranking it for these terms and capturing traffic from search. Human visitors, however, redirected to another commercial page.
Doorway pages offer little or no value to users and are most often hidden to users using cloaking techniques.
A common type of doorway page targets all local variations of a keyword. For example, a Mercedes dealership in Scotland might have a doorway page listing "Mercedes cars Edinburgh", "Mercedes cars Glasgow", "Mercedes cars Aberdeen" and so on, and so on...
To users, pages like this are useless, but search engines were once fooled by this technique and would rank the page giving black hat SEOs a sneaky way to get traffic to commercial pages.
Doorway pages are also commonly called bridge pages, gateway pages or portal page. They are something that the user is sent through to reach another page. The real landing page might not even have nothing to do with the original search query.
No. Doorway pages are a terrible idea. Search engines are constantly finding ways of discovering web pages with over-optimised keywords and link structures and most doorway pages are discovered as spam straight away.