These are the most commonly used java versions :
- JRE: Java runtime environment, what’s needed to run Java programs
- JDK: Java development kit, a JRE plus compiler and some additional tools
- Jave SE: Standard Edition, the API library that comes with every JRE and JDK for desktop use
- Jave EE: Enterprise Edition, additional APIs that extend the J2SE for business use, meaning mainly server applications – this includes JSPs
- Jave ME: Mobile Edition, a set of APIs (mainly a subset of J2SE) for mobile devices like phones
(The latter three are often also written as J2SE, J2EE and J2ME meaning “Java 2 ___ Edition” – Sun’s naming and versioning convention are rather confusing)
Note that all of these are basically specifications, and there are implementations from different vendors. For example, you can get a J2SE 6 JDK not only from Sun, but also from IBM and Oracle.