Intranet, Extra-net and Internet

Intranet : 
An intranet is an internal corporate networks built using internet and World Wide Web standards and products. It is used by employees of the organization to gain access to corporate information. An intranet is an inexpensive yet powerful alternative to other forms of internal communications. Since all information can be viewed on computer screes, this slashes the need for paper. It is also easy to access information., as all one needs is a computer with internet capabilities. To address security problems, organization require authorized users to have an id name password to access information.

Extra-net : 
An extra-net is a network that links resources of the intranet of a company with its customers, suppliers, or other business partners. It is built based on web technologies. It is a private network accessible through public infrastructure. Authentication and privacy are critical on an extra-net so that information is protected.

Internet : 
The internet is the largest computer network. It is a collection of interconnected networks all freely exchanging information. It is an add hoc linking of many networks that adhere to basic standards. The internet has beginnings with ARPANET ( a project started by the U.S Department of Defense in 1969 ).