This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Well, I would do a google search, it seems to have some interesting results, also doing a search fro Adaptor pattern might help.
However, basicly, its an adaptor, like a real world adaptor (like when you travel and everywhere has different electrical outlet sockets). It wraps an API to make the API easier to work with, to hide its complexity from the client.
By wrapping an API in an adaptor you provide a buffer between your client and the API, thus if the API changes all you need to change is your adaptor and not your client.