The term "Web farm" is used in different ways. It's commonly used to describe a Web hosting data center, such as those run by Exodus, or any ISP that offers collocation or Web hosting services. A Web farm can be any facility designed to connect dozens, hundreds or thousands of servers to the Internet. Those servers don't necessarily serve content for a single site. Some of the servers won't even be directly connected to the Internet, because a Web farm generally includes database and application servers that handle requests from the front-end Web servers.
With that said, "Web farm" is also used to mean a collection of Web servers that serve identical content for a single site. In this scenario, incoming requests are distributed between the multiple Web servers so that each Web server receives roughly the same number of requests.
This was first published in November 2002