What do they do?
R&D, generally. They develop new technologies, and integrate them into new products/processes.
Are they the same as Lockheed Martin Skunk Works?
Not really... they have a broader remit, if nothing else.
Military aircraft, space, airliners, materials science, numerical simulations (such as CFD) and various other (some seemingly irrelevant) software, the list goes on...
Hope that helps..?