Users employ client computers for word processing, spreadsheets, database access, and so forth. Most client computers also have software that enables them to connect to a network. Servers provide some service. Some servers process email; others process Web sites; others process large, shared databases; and some provide all of these functions or other, similar functions. They usually have multiple CPUs. Servers typically have limited video displays. Many servers have no display at all, because they are only accessed from another computer via a network. For sites with large numbers of users, servers are organized into a collection of servers called a server farm.