J2SE
Java Platform, Standard Edition (also known as Java 2 Platform) lets you develop and deploy Java applications on desktops and servers, as well as today's demanding Embedded and Real-Time environments. Java SE includes classes that support the development of Java Web Services and provides the foundation for Java Platform, Enterprise Edition (Java EE).
J2EE
Java Platform, Enterprise Edition (Java EE) is the industry standard for developing portable, robust, scalable and secure server-side Java applications. Building on the solid foundation of Java SE, Java EE provides web services, component model, management, and communications APIs that make it the industry standard for implementing enterprise class service-oriented architecture (SOA) and Web 2.0 applications.
J2ME
Java™ Platform, Micro Edition (Java ME) is the most ubiquitous application platform for mobile devices across the globe. It provides a robust, flexible environment for applications running on a broad range of other embedded devices, such as mobile phones, PDAs, TV set-top boxes, and printers. The Java ME platform includes flexible user interfaces, a robust security model, a broad range of built-in network protocols, and extensive support for networked and offline applications that can be downloaded dynamically. Applications based on Java ME software are portable across a wide range of devices, yet leveraging each device's native capabilities.
The Java ME platform is deployed on billions of devices, supported by leading tool vendors, and used by companies worldwide. In short, it is the platform of choice for today's consumer and embedded devices.