This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Abstraction used to describe how a particular system/library etc.. represents essential features of the same without going in to the complexity of the entire system/library. ADT (Abstract Data Types) are a good example of this.