Applet is component of AWT whereas JApplet is a component of Swing. JApplet is a Swing version of Applet.
An applet is a heavy-weight component, and JApplet is a light-weight component.
The swing components provide better look and feel than awt.
Swing components are derived from the javax.swing.* package and they are prefixed with a latter \'J\'(like JFrame, JButton, JApplet) Whereas applet is derived from the package java.applet.*