For example, when a client using a web browser like Internet Explorer or Netscape Navigator submits a search on a website, it is the web server that actually performs the search behind the scenes.
The web server itself has both hardware and software components. However, in common usage, when most people use "Web server", they are referring to the web server software that runs on the web server hardware.
The market leading web server software is Apache. The competitors to Apache include Microsoft Internet Information Server (IIS) and the Netscape Web Server.