An intranet is defined as a place that holds information on a network and is accessible to people within the offices of a firm. An extranet takes that definition a step further. Access is still limited to chosen users, but the information is now available from anywhere on the Internet, generally in a password-protected form. In other words, instead of company employees accessing company information strictly from within the walls of the office, employees and other authorized users can access company info from home, while on the road, from branch offices and so on.
For simplicity, in this book, we will call all the information available to chosen users an extranet (vs. an intranet or extranet). In the vast majority of cases, extranets are the way to go. Enabling specific users and assigning levels of access are possible with both intranets and extranets. However, rarely does it make sense to enable users to access information from only the office. The more accessible and immediate information is, the more valuable it tends to be. Hence, extranets are the way to go.
In everyday usage, intranet has come to mean the same thing as extranet, access to “inside information” available for selected users from anywhere on the network.