A computer that runs a Web site. Using the HTTP protocol, the Web server delivers Web pages to browsers as well as other data files to Web-based applications. The Web server includes the hardware, operating system, Web server software, TCP/IP protocols and site content (Web pages, images and other files). If the Web server is used internally and is not exposed to the public, it is an "intranet server" (see intranet). Contrast with Web client.|
The term "Web server" often refers only to the HTTP server software in the machine, which provides the Web site functionality. HTTP is the protocol of the Web, and HTTP server software, such as Microsoft's IIS and the open source Apache server, accepts requests from the user's browser and responds by sending back HTML documents (Web pages) and files. It also executes scripts that reside in the server (CGI scripts, JSPs, ASPs, etc.), which perform functions such as database searching and credit card authorization. See IIS and Apache.
One Computer or Hundreds
For a very small company, a single computer can contain the HTTP server along with an FTP server for file downloads, an SMTP server for e-mail and other Internet-related functions. In a large company, each service would be run in one or more dedicated servers, and a huge Web site may require hundreds of servers. See Web hosting and cloud computing.
Built Into Hardware Too
Web servers are not only on the Web. HTTP server software is commonly built into hardware to provide a control panel for configuring the device from any Web browser. Most network devices such as routers, access points and print servers actually contain a mini Web site for this purpose (see embedded Web server).
Web browsers communicate with Web servers via the TCP/IP protocol. The browser sends HTTP requests to the server, which responds with HTML pages and possibly additional programs in the form of ActiveX controls or Java applets.
This shows the server-side processes that can take place in a Web server (HTTP server) and application server. Since both can perform similar tasks, there is some overlap. The Web server and application server can be in the same machine or in separate computers. See