CERN is the European Organization for Nuclear Research, the world's largest particle physics centre. Here physicists come to explore what matter is made of and what forces hold it together.
CERN exists primarily to provide them with the necessary tools. These are accelerators, which accelerate particles to almost the speed of light and detectors to make the particles visible.
Founded in 1954, the laboratory was one of Europe's first joint ventures and includes now 20 Member States.
Part is in Switzerland, part in France across the border. CERN is not a Swiss institute, but an international organization. We are very close to Geneva's intercontinental airport.
This link provides a detailed view of CERN: http://cern.ch/area-map/AreaMap.html
And yes, this is the same CERN as in Angels and Demons.