intranet

"a network based on tcp/ip protocols belonging to an organization, usually a corporation, assessible only by the organixation's members, employees, or others with autorization"

The intranet are in-house , tailor-made internets for use within the organisation and provide limited access(if any) to outside services and also limit the external traffic into the intranet(if any)
An intranet might have access to the internet but there will be no access from the internet to the organisation's intranet
An intranet's web sites look and act just like any other web sites, but the fireball surrounding an intranet fends off unauthorized access
Like the internet itself , intranets are used to share information.Secure intranets are now the fastest-growing segment of the internet because they are much less expensive to build and manage than private networks based on proprietary protocols