Internet, intranet and extranet are both related and different, mainly in the following aspects: (1) In terms of operating authority, the services provided by the Internet have little or no control over users, while the intranet and extranet have very strict control over authority. (2) In terms of content, the information pages provided by the Internet are mainly static, while the information content provided by the intranet and extranet is mostly related to the database, that is, the information content provided is dynamic and changes with the change of the underlying database. 3) In terms of service objects, Internet services are for global users, intranet services are for employees of enterprises, and extranet services are for employees of trading partners. (4) In terms of connection mode, the Internet emphasizes the connection between websites of various institutions, and enterprises and consumers without transactions are its business scope; Extranet emphasizes the connection between enterprises, and its business scope includes trading partners, partners, affiliated companies, sales stores and major customers. Intranet emphasizes the connection of various departments within the enterprise, and its business scope is limited within the enterprise.