How is the surface web created?
Search engines construct a database of pages on the Internet through programs called web spiders. The spider receives a copy of each page and catalogues it, keeping the appropriate information for quick retrieval later. When a new page is linked, it is eventually inspected by the spiders and added to the list of reachable pages; the surface Web.
Any pages that cannot be found in the surface web manner are part of what is called the deep web.