Sometimes, the "dark" Web is erroneously used to mean the deep Web (definition #2 below). See dark Web
Content on the Web that is not found on a Google, Yahoo or Bing search because it has been coded to keep the search engines from indexing it. Deep Web content is thousands of times larger than the public Web ("surface Web").
Also known as the "invisible Web," viewing such content is accomplished by going to the desired website and typing the query into the site's search box. Countless sites make their content available to the public in this manner, and registration may be required. Such sites may be free or paid as well as password protected.
Deep Web content resides within databases on the site's servers and not within the actual Web pages. However, search tools do exist that can query deep Web content. See LexiBot
See deep link