What is the function of the enzyme ATP synthase in mitochondra

Since this is not my area of expertise, I searched Google under the key words "ATP synthase mitochondra" to get these possible sources:

(Broken Link Removed)
http://en.wikipedia.org/wiki/ATP_synthase
http://www.mrc-dunn.cam.ac.uk/research/atpase.html

I hope this helps. Thanks for asking.