INTERNET USE

The Internet is the world's computer networking system, which allows you to use a computer to search for information and communicate directly with anyone on that network.
An intranet is a smaller, closed (e.g. in the sense of an organisation) version of the Internet that is accessible only by registered users of the intranet.
An extranet is a version of an intranet where the internal network of the institution can be accessed by registered external users.