Based on the restrictions of availability, architecture and protocol, the entire web world can be classified into- Surface, Deep and Dark Web. Surface web are the sites, software or networks openly available to the public for use or share. The common examples are the Wikipedia, Google maps or the public portals run by the govt. organizations.
A deep web is the realm restricted only to the members. However, anybody eligible & willing can join and participate. To avert unauthorized entries, those are protected by usernames, passwords and other methods like-OTPs. The most common examples are- the E-mails, business and banking services etc. Contrary to the surface and deep web and
A Dark Web is the part invisible to the internet users. That is un-indexed, un-localized and anonymous. The broad categorization is illustrated below-