You might like to start with:
The Packages tutorial at java.sun.comChapter 5 of Thinking In Java, seeing you're reading this already. I think you'll find these sites more thorough and readable than asking questions here - at least for the fundamentals of packages. If you have any specific questions about them though, people here will be more than happy to help you.
Cheers,
--Tim
[ April 27, 2004: Message edited by: Tim West ]