For practical purposes, think of an Intranet as a private collection of computer files that are accessible through a Web browser such as Firefox or Internet Explorer. Typically, these files are stored on a local area network (LAN), and they're accessible to users logged into the LAN but not accessible over the Internet. If your organization has a LAN, you're well on your way to having an Intranet.
The computer files making up your organization's Intranet could be whatever you want. While Web pages (i.e., HTML documents) are the most common, word processing documents, spreadsheets, Adobe Acrobat (PDF) documents, etc., can all be part of the Intranet.
