Internet is something that is wide spread and but what if it contracts and has information only about you and your firm and is accessible to only authorized members of your organization this is where an intranet comes into existence. An Intranet looks and acts like a website but the difference arise at point that there exists a firewall that fends off unauthorized access. Their main use arises for sharing of information and is much less expensive to build and manage than private networks based on proprietary protocols.
Advantages of Intranet
Intranet is useful only for the members of one single organizations but if the reach of intranet extends to members outside then that refers to extranet. But 'outside' we mean an extranet provides various levels of accessibility to outsiders (suppliers, vendors, partners, customers). An extranet is accessible only if the user has a valid username and password. His identity determines which parts of the extranet he can view. Extranets can be viewed as a very popular means for business partners to exchange information.