Load balancing is dividing the amount of work that a computer has to do
between two or more computers so that more work gets done in the same
amount of time and, in general, all users get served faster. Load balancing
can be implemented with hardware, software, or a combination of both.
Typically, load balancing is the main reason for computer server clustering.

On the Internet, companies whose Web sites get a great deal of traffic
usually use load balancing. For load balancing Web traffic, there are several
approaches. For Web serving, one approach is to route each request in turn
to a different server host address in a domain name system (DNS) table,
round-robin fashion. Usually, if two servers are used to balance a work load,
a third server is needed to determine which server to assign the work to.
Since load balancing requires multiple servers, it is usually combined with
failover and backup services. In some approaches, the servers are distributed
over different geographic locations.