The difference between a Intranet and a Extranet is the access method. They have similar function, resources and general philosophy, that is giving easy and safe access to the requested information.

Extranet is born when a company wants to let some people or groups of people have access to a determined information in the Intranet. Without making it public, it makes accessible to other people that may need it or with whom it has commercial businesses. The clearest example is the access a company gives for a part of his clients and suppliers.