There is no technical difference between the Internet and the intranet, except that not everybody is allowed to connect to an intranet.
Intranet is an application of the Internet technology to a closed network.
It provides a relatively cost efficient way to connect and manage corporate networks and distributed information. The surprising speed by which intranets has grown among corporate users demonstrates the strength of the Internet networking. The compatibility of corporate intranets with the Internet will be a significant factor in the digital economy. In a sense, producer and seller information is readily accessible by outsiders, making it easy to manage and disseminate information to consumers. Intranets use domain names that may not be recognizable by outside servers.