There are several editions of Java. There's Java SE (Standard Edition), which is the standard Java runtime environment for desktop computers. There's Java ME (Micro Edition) which is Java for small devices such as cell phones and PDA's.
And there's Java EE, which builds on top of Java SE. Java EE contains a number of extra API's which are especially useful for developing software in business environments, for example for software running on servers where there are many users using a large system.