Not a physicist? We hope that reading through the pages linked from the "About Neutrinos" and "About Borexino" menu items at left will provide a decent introduction to neutrinos and neutrino detectors. You may also find the press releases from the National Science Foundation and Princeton University interesting.
Borexino is an international experiment, located deep underground in the Gran Sasso National Laboratory of Italy. The experiment is dedicated to the observation of low-energy solar neutrinos. The Borexino collaboration, whose main web page is here, includes a very active group at Princeton University. Primary goals of the experiment are observation of the mono-energetic 7Be neutrinos at 862 keV, and precise measurement of their rates in order to test current models of the Sun and of neutrino oscillation. The detector came online in May, and our first results are now available on arXiv and published in Physics Letters B.
Secondary goals that are perhaps a bit more of a reach include observation of pp, pep and CNO-cycle solar neutrinos, as well as detection of geoneutrinos produced by radioactive isotopes in the Earth's crust, and observation of neutrinos from a nearby supernova (if we are fortunate enough to have one occur).
While detectors such as SNO, SuperK and KamLAND have observed higher energy neutrinos (both from the sun and from nuclear reactors and radioactive isotopes in the Earth's crust), until now no one has been able to make real-time observations of the lower energy neutrinos that make up 99% of the Sun's output. The breakthrough that permits Borexino to do so is an emphasis on the ultimate in radiopurity, both in all hardware components of the detector and in the scintillator where the interactions that permit us to detect the neutrinos take place.