Intranet / Extranet
An Intranet is a network based on the internet TCP/IP open standard. An intranet belongs to an organization, and is designed to be accessible only by members and employees of this organization or other authorized parties. The website of an intranet looks and operates just like other websites, but has a firewall surrounding it to fend off unauthorized users. Intranets are used to share information. Secure intranets are far less expensive to build and manage than private, proprietary-standard networks.
Extranet refers to a group of websites, belonging to independent entities that are combined together to allow information sharing. Extranet is opposed to an intranet, which is a private site accessible only to employees of an entity. Extranets are used in supply chains to allow more effective communications. They are replacing proprietary standard networks that are considerably more expensive to establish, and therefore were only used by large organizations.
