There are basically 3 Java releases.
- Micro Edition (ME)
- Standard Edition (SE)
- Enterprise Edition (EE)
Sun made a lot of changes to the Java platform library and VM between versions 1.1 and 1.2, enough so that they decided to call the result "Java 2" instead of plain Java, but without actually changing the version numbers. Thus "Java 2" starts at version 1.2. This is a confusing Sun-ism; they have done similar things with their operating system products. Anyway, not too long after, Sun started packaging a collection of additional Java components targeted at "enterprise computing" -- servlets, messaging, "Enterprise JavaBeans," etc. -- as "Java 2 Enterprise Edition", or J2EE for short. In order to distinguish the original, base Java 2 package, it was rebranded to "Java 2 Standard Edition," or J2SE. (This all happened rather more than three years ago, by the way.) "Java 2 Enterprise Edition" is a bit of a misnomer, as it suggests that J2EE is an alternative to J2SE. This is not the case. Rather, J2EE is a collection of /extensions/ to J2SE.
With the release of version 1.5 of the Java platform library and developer kit, Sun has done it again, announcing that the changes are so major that the result is now to be known as "Java 5". In conjunction with that change, they are also moving to call the core package simply "Java Standard Edition," and to call the enterprise package simply "Java Enterprise Edition."
Also, though you didn't ask, "J2ME" is "Java 2 Micro Edition," a Java library and runtime environment for small devices such as cell phones. J2ME is more deserving of a designation as a different "edition" of Java than is J2EE. I'll leave it at that.
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Java Platform, Enterprise Edition
Java Platform, Standard Edition
Java Platform, Micro Edition
So if you download & install NetBeans Java (214 MB) one, you have everything you need. (SE one is also enough for you to start if you like). Language wise, it's all same. Just differences of libraries.
