The Deep Web refers to World Wide Web

World Wide Web

The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...

 content that is not part of the Surface Web

Surface web

The surface Web is that portion of the World Wide Web that is indexed by conventional search engines. The part of the Web that is not reachable this way is called the Deep Web. Search engines construct a database of the Web by using programs called spiders or Web crawlers that begin with a list of...

, which is indexed

Index (search engine)

Search engine indexing collects, parses, and stores data to facilitate fast and accurate information retrieval. Index design incorporates interdisciplinary concepts from linguistics, cognitive psychology, mathematics, informatics, physics, and computer science...

 by standard search engine

Search engine

A search engine is an information retrieval system designed to help find information stored on a computer system. The search results are usually presented in a list and are commonly called hits. Search engines help to minimize the time required to find information and the amount of information...

s.

Mike Bergman, founder of BrightPlanet, credited with coining the phrase, has said that searching on the Internet today can be compared to dragging a net across the surface of the ocean: a great deal may be caught in the net, but there is a wealth of information that is deep and therefore missed.