Java Runtime Environment - If you don't plan to create ["Java"] apps yourself, then this is enough.
The Runtime Environment for Linux contains the Java Virtual Machine (["JVM"]), Java core classes, and supporting files. It does not contain any of the development tools (such as appletviewer or javac) or classes that pertain only to a development environment.
The Java 2 Runtime Environment is smaller than the Java 2 SDK
See: for creating Java apps, ["SDK"]