"Java" refers to both a language and a platform. The runtime and libraries that comprise the platform are based on the Java language and come in 3 flavors:
Java SE (Standard Edition) Formerly J2SE but renamed to Java Standard Edition when the Java 2 convention was dropped with the release of Java 5 (formerly J2SE 1.5). It contains a good all-around mix of general purpose libraries including JDBC(Java Database Connectivity),JNDI(Java Naming Directory Interface), RMI (Remote Method Invocation), AWT and Swing.
Java SE (Standard Edition) Formerly J2EE (see above). It includes Java Standard Edition plus most of the other Java technologies including JavaMail, Activation, JAXB (Java API for XML Binding), Servlets, JSF (Java Server Faces), JMS (Java Messaging Service), EJB (Enterprise Java Beans), and others. Most of the APIs are very component-oriented and are intended to provide pluggable interfaces for business components to form robust, distributed internet applications.
Java ME (Micro Edition) Formerly J2ME. It includes most of Java SE and some additional APIs for handheld devices.
"Java Enterprise"is based on Java, but includes a larger set of libraries than Java Standard Edition, which to most people is synonymous with the word "Java." Note that many of the technologies featured in Java Enterprise Edition are available separately and can be added to the Java Standard Edition platform as needed.