The certificate is for finishing the Google Power Search Course. Actually I finished it last week but assessments could be taken until a few days ago. It was Google first attempt at a MOOC and they did quite a nice job. You can still view all the material and browse the forums and view some Google+ hangouts with search experts that were recorded but it's no longer possible to do the assessments anymore and, thereby, earning the certificate. I suggested in the final evaluation that Google should consider making the course anytime, anywhere available.
The certificate looks nice: