Packages - Installing  
A .jar file is basically a .zip file plus a little extra information. This file may contain one or more packages, and all the classes in them. If it knows where to find the ..

Packages - Defining  
Packages correspond to directories in the file system..

Packages - Importing  
Multiple classes of larger programs are usually grouped together into a package..

Directories and Files  
Put all source files into a directory, one class per file.

CLASSPATH  
CLASSPATH tells Java where to search for programs..