Java Applet VS Java Application

Application is a Java class that has a main() method. An applet is a Java class which extends java.applet.Applet. Generally, application is a stand-alone program, normally launched from the command line, and which has unrestricted access to the host system. An applet is a program which is run in the context of an applet viewer or web browser, and which has strictly limited access to the host system. For instance, an applet can normally not read or write files on the host system whereas an application normally can. The actions of both applets and applications can be controlled by SecurityManager objects.

Applets may communicate with other applets running on the same virtual machine. If the applets are of the same class, they can communicate via shared static variables. If the applets are of different classes, then each will need a reference to the same class with static variables.

from http://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol1/tay/app.html