Sometimes referred to as Bridge pages, Gateway pages, Portals, etc. Traffic alone defines the success of any web site on the world wide web. Sure, there are overnight success stories where someone's web site went from less than ten unique visitors a month all the way to a million hits a day, but that's always been due to some very lucky media exposure. Notice I keep saying traffic.
Traffic is what keeps a site alive.
Your job is to direct that traffic to your site. That brings us back to Doorway pages. That's what a doorway page is for your site. A traffic director. Not just any old traffic director mind you, but a highly optimized and up to date traffic director.