To add to what Layne said...
In simplistic terms, J2SE (
Java 2 Standard Edition) is
the Java programming language and its core API's (Application Program(ming) Interface). J2EE (Java 2 Enterprise Edition) is a group of API's that can be used in addition to (or "on top of") J2SE. It contains API's that are usually used for larger applications, multi-tiered (or layered) applictions or server side applications. It contains API's (such as the Java Database Connect (
JDBC),
Servlet,
JSP, Enterprise JavaBeans, and Java Mail API's as some examples) that are not part of J2SE and are therefore not contained in the Java Runtime Environment (JRE)installed on a typical client. Many J2EE API's are implemented by third parties in things such as Web Servers, Application Servers, Database Connection Libraries, etc.