The primary purpose of a network is to allow sharing of limited resources. In our hypothetical home, we plan on sharing files and printers. There are several files on the business computer that would be beneficial to access from the portable. Also, in the office there is a laser printer and an inkjet printer, which the kids would like to use. If this was the only sharing which was required, special file transfer software and spooling software could be installed, implementing a highly specialized network. With today's operating systems being network aware, building a peer-to-peer or client/server Local Area Network, or LAN, is actually easier than these specialized networks of yesterday.
There is another compelling reason to implement a LAN in addition to the file and printer sharing requirements. Each of the computers in the home has a modem and is capable of accessing the Internet through the family Internet Service Provider (ISP), but each must do so one at a time. With a LAN and some special software, called a proxy, the entire family can simultaneously share a single Internet connection.