In web applications, there are usually at least two computers involved: a client computer that requests a particular web page, and a server computer that processes that request and serves the page back to the client. (See Figure 16-1.)
In the diagram in Figure 16-1, we can see the process of requesting a web page. Recall that we looked at this briefly in Chapter 1. It starts on the client machine with our website visitor entering or choosing a Universal Resource Locator (URL) in a browser. The URL tells the browser which server machine on the Internet to request the web page from, together with a path for the server directory that the web page is located in and of course the file name of the web page.
Server-side processing can involve a variety of tasks, such as processing information sent by the user in a web page's form, accessing a database to retrieve or store information, running a program on the server to check credit card details before telling another computer to send goods to a customer, and even sending e-mails. With the right components installed, a server can undertake a vast range of tasks.
Before we start looking at the ASP objects, we need to install a server. Normally the web server and user's browser would be on different machines, but there's no reason they can't be on the same machine. In fact, this is very handy for development purposes.