Extranet:

An Extranet is an intranet that extends onto the Internet.

An extranet is a private network that uses the Internet protocol and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses. An extranet can be viewed as part of a company's intranet that is extended to users outside the company. It has also been described as a "state of mind" in which the Internet is perceived as a way to do business with other companies as well as to sell products to customers.

An extranet requires security and privacy. These require firewall server management, the issuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtual private networks (VPN) that tunnel through the public network.

Companies can use an extranet to:
      1. Exchange large volumes of data using Electronic Data Interchange (EDI)
      2. Share product catalogs exclusively with wholesalers or those "in the trade"
      3. Collaborate with other companies on joint development efforts
      4. Jointly develop and use training programs with other companies
      5. Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks
      6. Share news of common interest exclusively with partner companies