The term client machine refers to a user's computer that is connected to a network and accesses another computer, called a server, to request various kinds of resources, to save data or to run certain programs or perform certain functions. Sometimes the term "client" is used interchangeably with client machine, but client is a less specific term that can also refer to a computer application rather than an actual computer. The machine is sometimes called the requesting machine, because it requests files or other data from a server, sometimes called the supplying machine. A client computer usually has a user interface that is supplied by the client operating system, for example Unix, Windows or Linux. Different kinds of networks can be used to connect a client to a server, for example a local area network (LAN) or wide area network (WAN).
A client machine can be a laptop, office workstation, IBM-compatible personal computer (PC), Mac, or other individual computer that relies on interactions with a server to perform its functions. Sometimes a client download is required for the machine to interact with the server. This means a program has to be downloaded from the server and installed on the machine. For example, individuals playing online computer games usually need a client download to enable them to play the game using data supplied by the game company's servers.
A common example of a client machine is in an office setting where an individual employee can use his or her workstation, either in the office or remotely from other locations, to access disk storage space, data, or other resources from company computers acting as servers. Today, client computers can usually run their own programs without accessing the server. However, in the early days of computers, some client machines were so-called dumb terminals, unable to run any programs without input from a server.
Examples of different types of client machines are fat client, thin client, and hybrid client. A fat client refers to a machine that is able to perform much of its own processing, and does not require continuous contact with the server to perform its functions. Thin clients rely more heavily on servers. A hybrid client computer, sometimes called a network computer, usually performs much of its own processing, but often uses a server to store data. Some hybrid client computers are so-called diskless nodes that do not have permanent hard drives and use centralized storage on the server instead.