The AWT defines two different kinds of containers, panels and windows. Panels are subclasses of java.awt.Panel . A panel is contained inside another container, or perhaps inside the web browser's window. Panels do not stand on their own.
Applets are panels.
Windows are subclasses of java.awt.Window . A window is a free-standing, native window. A frame is an instance of a subclass of java.awt.Frame . It represents a normal, native window. A dialog is a subclass of java.awt.Dialog .