I am really surprised when reading through the forums on a daily basis, the number of people that think or end up using doorway pages for their websites and think that it is alright. Essentially, never try to trick the search engines and always go for quality!
Doorway pages have many different names, gateway pages is another popular name as well, other common names are portal pages, jump pages and entry pages. The purpose of these pages is to rank highly in the search engines and draw traffic for your targeted keywords. Sounds good right? These pages are highly frowned upon by all the search engines, and is a sure way to get your site banned. They are basically designed for the search engines and not for humans.
The Problem with Doorway/Gateway Pages
Doorway pages are far too generic and do not provide and useful content for the reader. A Doorway page serves as a connector between the actual page the website owner intended you to see. Often what would happen is a page would be created focusing typically on 1 – 3 keyword phrases per page and those links would then point you towards the page that has all the goodies and info you really want. Also, it was common for these pages to be linked from the home/index page with hidden links (this is another great and sure way to get your site banned).
Eventually you will get caught and all it takes is a competitor or a viewer that finds your page with these spam pages and report it to the search engine. Many search engines these days have pages/email addresses setup for reporting spam to help them improve the results in the search engine.
While you may think it provides some kind of short term benefit, sooner or later you will get caught, and all the time and money you invested is now gone and you have to start over again from scratch. I would highly highly advise you to stay away from doorway pages!