Java is a high-level, object-oriented, multi-platform programming language developed by Sun Microsystems.

J2SE
Java Platform, Standard Edition (J2SE) provides a complete environment for applications development on desktops and servers and for deployment in embedded environments. It provides the basis for security, database connectivity and more. Desktop Java enables you to write rich, highly interactive client software. J2SE also serves as the foundation for the Java 2 Platform, Enterprise Edition (J2EE) and Java Web Services.

J2EE
Java 2 Platform, Enterprise Edition (J2EE) defines the standard for developing component-based multitier enterprise applications. J2EE simplifies building enterprise applications that are portable, scalable, and that integrate easily with legacy applications and data. J2EE is also a platform for building and using web services. It incorporates web services standards such as those in the WS-I Basic Profile. This means that web services in a J2EE-compliant environment can interoperate with web services in non-J2EE environments such as .net.

J2ME
The Micro Edition of the Java 2 Platform provides an application environment that specifically addresses the needs of commodities in the vast and rapidly growing consumer and embedded space, including mobile phones, pagers, personal digital assistants, set-top boxes, and vehicle telematics systems.

Java Card
Java Card technology provides a secure environment for applications that run on smart cards and other devices with very limited memory and processing capabilities. Multiple applications can be deployed on a single card, and new ones can be added to it even after it has been issued to the end user. Applications written in the Java programming language can be executed securely on cards from different vendors.