This is a web site page designed as an entrance to a web site. For example a web site may produce and sell red wine from France, so that web site might create a doorway page for the area of France the red wine is from. So when someone types "red wine from the South of France" at a search engine they will get directed to the doorway page which will then direct them to main web site page. The problem with doorways is that search engines like Google see them as spam and can ban a web site for using them.