“The OPERA experiment has reached its first goal: the detection of a tau neutrino obtained from the transformation of a muon neutrino, which occurred during the journey from Geneva to the Gran Sasso Laboratory,” added Lucia Votano, Director Gran Sasso laboratories. “This important result comes after a decade of intense work performed by the Collaboration, with the support of the Laboratory, and it again confirms that LNGS is a leading laboratory in Astroparticle Physics”.
“This is an important step for neutrino physics,” said CERN Director General Rolf Heuer. “My congratulations go to the OPERA experiment and the Gran Sasso Laboratories, as well as the accelerator departments at CERN. We’re all looking forward to unveiling the new physics this result presages.”
Basically, in more simple terms, they send a beam which is 100% made out of muons from CERN, and it arrives at the Gran Sasso laboratory, and they detected a tau particle.
Neutrino oscillation is basically that a neutrino is measured to be one "flavour" [that's the scientific term] (electron, muon or tau, as you can see above.), and when they measure it later, it's another flavour. In this case it went from a muon to a tau particle.
What impact does this have on Physics? It proves that there have to be other types of particles and/or matter which we currently don't know about.
So by accelerating a particle, it somehow turned into a different flavour of the same particle?
Well, sort of. They accelerated the particle (Particles, actually, because manipulating a single one is borderline impossible), focused them into a beam, and shot them through Earth into that other lab. Along the way it became a Tau Neutrino.