The internet, intranet, and extranet are all different types of networks in terms of accessibility. But first, what is a network?
A network is a group of computer resources or computers connected to share resources, communicate, etc. These computers can be connected with cables or wirelessly.
So how does this relate to the internet, intranet, and extranet? Computers can be connected without being connected so that they can communicate with every network available. However, some are connected in such a way that they only want to communicate with certain networks or groups of computers. And some are connected in such a way that they want to remain private, but still be able to communicate with public networks.
The internet is a network that is accessible to everyone. It is known as the global village because it brings everyone close regardless of distance barriers. A typical example is the World Wide Web (WWW).
The intranet is a kind of network accessible to only the computers on that network. This means it is a private network. It is normally used by institutions that have information that should not be shared with the public.
Extranets are also private networks. The difference, however, is that it gives some stringent access to some public users. These users might provide value, profit or help run the organization. They could be customers, suppliers, agents, etc.