A small program that runs on a server. The term usually refers to a Java applet that runs within a Web server environment. This is analogous to a Java applet that runs within a Web browser environment.
Java servlets are becoming increasingly popular as an alternative to CGI programs. The biggest difference between the two is that a Java applet is persistent. This means that once it is started, it stays in memory and can fulfill multiple requests. In contrast, a CGI program disappears once it has fulfilled a request. The persistence of Java applets makes them faster because there's no wasted time in setting up and tearing down the process.
Inside the Java Web Server White paper from Sun Microsystems that provides an overview of the Java Web server, Java servlets, and the JavaServer architecture.
Servlet FAQ Short FAQ from the JavaServer Product Group.
