There are three parts to an Internet connection:

1. The client
2. The server
3. The connection linking them

This configuration is called the client/server model. In the client/server model, one program requests a service from another program. The client makes a request; the server answers the request with a service. The client and server communicate with each other by both physical (hardware) and logical (software) links.

A client consists of:

1. A desktop computer (hardware)
   
2. A program (software) that requests information from the server

The program usually resides on a personal computer. An example of such a program is a Web browser. When you want to see a particular Web site, the browser handles your request.

Typically a server is a remote device shared by many users. A server can be:

1. A machine that stores a particular resource you want to use, such as a database or Web pages
2. A machine that performs specific functions such as sending and receiving e-mail

Servers are available commercially from companies including Sun Microsystems, Sequent, IBM, Unisys, Dell, Compaq, and NCR. The figure below illustrates the relation between a client and server connected through local and regional Internet Service Providers (ISPs).