Doorways is a term used in SEO to refer to a deceptive technique in which a set of specialized pages (often called doorway pages) is created. These pages are highly optimized for very specific and often diverse keyword queries with the sole purpose of achieving high rankings in search results.
Despite their high search engine optimization, these pages do not contain any useful, original or quality information for the end user. Their only function is to serve as an intermediate point or “doorway”.
As soon as a user or search engine bot loads such a page, an automatic redirect is triggered to the main website that is actually being promoted. Since this practice intentionally manipulates search results and provides a poor user experience, it is considered a Black Hat SEO technique and is severely punished by search engines with deindexing or Ban.