Protons are accelerated in opposite directions almost to the speed of light (actually
99.999999% of the speed of light) and then brought together to collide at four points on the ring. When they collide they recreate the energy conditions of the early universe one billionth of a second after the Big Bang, when the universe was the size of a football!
Funnily enough, the total energy liberated in this collision is quite small, about the same
as the energy liberated when a fly flies into a brick wall. However, because it occurs over such a small range, the energy density is enormous.
Much more information on the LHC can be found from the
CERN home page
or from their information pages about
the LHC .