An applet is a special kind of Java program that a browser enabled with Java
technology can download from the internet and run.
An applet is typically embedded inside a web page and runs in the
context of a browser. An applet must be a subclass of the
java.applet.Applet class. The Applet class provides
the standard interface between the applet and the browser environment.
Swing provides a special subclass of the Applet class called
javax.swing.JApplet. The JApplet class should be used
for all applets that use Swing components to construct their graphical user
interfaces (GUIs).
The browser's Java Plug-in software manages the lifecycle of an applet.