differences between internet,intranet and extranet

There's one major distinction between an intranet and the Internet: The Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but as a rule it's protected by a password and accessible only to employees or other authorized users. From within a company, an intranet server may respond much more quickly than a typical Web site. This is because the public Internet is at the mercy of traffic spikes, server breakdowns and other problems that may slow the network. Within a company, however, users have much more bandwidth and network hardware may be more reliable. This makes it easier to serve high bandwidth content, such as audio and video, over an intranet. (unless you work for the United States Marine Corps. Then you don't get to watch video's. And they Block 80% of any kind of "fun" or entertaining website available on the Internet) The Extranet is a portion of an organization's Intranet that is made accessible to authorized outside users without full access to an entire organization's intranet.