EJB

A Java-specific component model that operates in the context of Java 2 Enterprise Edition application architecture
Based on a specification which is implemented as application servers (BEA WebLogic, IBM WebSphere, iPlanet Application Server) and databases (Oracle 8i, 9i, Sybase jaguar, IBM DB2)
Flexible (Providing message-driven EJB) and portable (introducing an EJB query syntax to replace proprietary mechanisms)
EJB server provides the underlying support for security, transactions etc and is shared between all EJBs
Two primary EJB types:
session beans: conceptually similar to transactional COM+ components
entity beans: a mapping of underlying data and are intended to be longer-lived

"The EJB 2.1 specification enhances the EJB architecture with support for Web services. Enterprise developers can implement and deploy Web service applications with the same level of ease as other server-side applications.

In addition, EJB 2.1 provides a container-managed Timer Service; enhancements to EJB QL -- the declarative language for container-managed persistence -- to support aggregate and order-by operations; and a generalization of message-driven beans to support additional messaging types.

The EJB 2.1 specification effort is being conducted as JSR-153 under the Java Community Process (JCP) program."

-- java.sun.com