This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
Heavy weight components (AWT) are known to the operating system. They consist of a "peer", which is the implementation of the component in the operating system, and a Java object which manages the peer.
Light weight components (Swing) are drawn entirely within Java; the operating system is not aware of or responsible for their existence.