All AWT components are heavyweight components.
Heavyweight Components :- are those components which have a native peer classes( for a particular platform )associated with it.
These component do not know how to draw themselves. Whenever a heavyweight component is drawn/redrawn it sends a signal to it's peer class and this peer class draws the component with native look and feel. A button in windows always has the same look and feel. The same button in Motif will look like Motif buttons do.
So the look and feel of these component are tightly bound with the platform, which uses more system resources.
Swing components are Lightweight.
Lightweight components :- These components that know how to draw themselves so no peer classes are involved and hence they can have a consistant look and feel. Moreover since there is no operating system involvement these are more efficient.
Here is a short tutorial on the differences:
http://developer.java.sun.com/developer/onlineTraining/GUI/Swing1/ [This message has been edited by Cindy Glass (edited January 23, 2001).]