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.
Reflection and introspection refer to the same concept, of looking up a Class programmatically and inspecting the class like how many methods does it have, what are the super classes, implemented interfaces etc....in short you can actually "read" a class. Not only that, you can also use this concept successfully to create Applications etc. a good place to start is here(Reflection Tutorial)
A lot of Frameworks depends on reflection like Struts etc, and soon you will appreciate the many ways you can use reflection.