Servlets are Java based applications for server side application.
Similar to any CGI script that captures and processes data, the JAVA language is also used to create server side programs that allow for complex data manipulation.
Java Servlets are Java applications that run on a web server. They are similar to other CGI web server applications See http://java.sun.com/products/servlet/whitepaper.html
A servlet is an application or a script that is written in Java and executed on a server, as opposed to on a client. It is analogous to CGI, although servlets are more than simply CGI scripts written in Java.
A Java application that is designed to execute on a webserver instead of on the client's computer. Servlets can be used in the same way that CGI programs...
Extensions that enable all Java servlet metafunctions, including instantiation, initialization, destruction, access from other components, and configuration management. Java servlets are reusable Java applications that run on a web server rather than in a web browser.
Java Servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems.