What is a gateway page? What is a doorway page? Is there a difference between them? What is the difference?
As you can see, this could get complicated....... so I propose starting off simple - the definition of gateway and doorway pages is interchangeable; there is a difference between them, but only depending on who you listen to. What are gateway and doorway pages (and entry and portal and bridge pages....)
The common (and commonly interchangeable) definition of a gateway page is that which leads visitors into a site, offers a menu of all other pages available on the site, but may not necessarily be a structural part of the whole site. Sort of like a Gateway really, it leads visitors into a house, gives them a taste of the grandeur to be enjoyed within, but isn't actually part of the main building.
So moving on to the doorway page; this is sometimes defined as a page with the sole purpose of improving a web site's position amongst search engines, and so drawing more traffic into the site. The techniques used by doorway pages to improve the ranking of an entire site are less clearly defined, but presumably include the usual suspects (keyword placement, relevant content etc.)
Although if you take a step back from the over-analysis it is just possible that the definition of all of these pages is right there in front of you; gateway, doorway, portal, bridge,entry - they are all pages that lead a visitor deeper into a website.
So what is the difference?
Whilst I don't want to stand on the fence on this issue (we have enough furniture to deal with) it is possible that there is no absolute definition of these words. Research suggests that one of the pages could be designed to attract the visitor, and the other designed to attract the search engine.
This would be a nice definition (you can decide which one is the gateway and which is the doorway depending on your mood) if again, the two didn't basically amount to the same thing.
Unless one of these techniques involved some black hat activity (keyword stuffing etc.) to attract the search engines (which would backfire as spam anyway), or some serious graphics overload to put off the search engines (which might be ok if some relevant content were thrown in), the general consensus is that what is good for the search engine is good for the visitor.
So what is the answer?
It is little wonder that these terms are often confused, they kind of seem to mean the same thing. It gets even worse when you throw 'portals' and 'bridge' and 'entry' pages into the mix.
So the ultimate answer I can offer is this; gateway, doorway and portal pages are all ways of getting into a website. Like any published web pages they should contain keywords and be optimised for search engines and visitors alike to get maximum visibility in search engine results.