Refer to http://java.sun.com/ for additional information concerning Sun Java Technology.
Detailed information related to this particular package can be found at http://java.sun.com/j2se/.
SUMMARY:Java 2 Standard Edition.
You should have a full 1.4 or later capable Java Runtime Environment (JRE) at a minimum. However, as a developer, you should just go for the Java Standard Edition (or whatever they are calling the developer version now). It seems that the 1.4.2 release comes bundled with the xalan-j tools from the Apache project (which will save you from adding this package separately).
We can't offer too much guidance towards installation. The best we can do is refer you to the web site: http://java.sun.com/j2se/. Good luck.