What does J2EE comprise of?

J2EE is a collection of APIs that can be used to build such systems, although this is only half of the picture. J2EE is also a standard for building and deploying enterprise applications, held together by the specifications of the APIs that it defines and the services that J2EE provides. In other words, this means that the "write once, run anywhere" promises of Java apply for enterprise applications too:

• Enterprise applications can be run on different platforms supporting the Java2 platform.
• Enterprise applications are portable between application servers supporting the J2EE specification.

J2EE which is now Java EE stands for Java Enterprise Edition!

Java2.0 for Enterprise Edition