What is it just exactly ??
Overall... The LHC consists of a 17 mile ring of very cold and very powerful magnets. These magnets bend a beam of particles around in a circle and speed them up so fast that well,, you wouldn't be able to keep up :).. Once they are literally almost going light speed they collide them with particles going in the other lane of traffic hitting them head on. These collisions hopefully create the most energetic explosions ever produced by man but are very controlled and kept in a very tiny area. The debris from the collisions sprays out in all directions but in a very tell tale way that lets physicists figure out what the debris was made made of. Some of this "debris" could change our understanding of the world forever. The process of figuring out what the debris is made of is done in a detector.
The LHC machine has 4 primary detectors.
ATLAS - This will look for things that will either confirm our understanding of physics or prove we need a new theory. It will try and figure out why things have mass and will study other dimensions if they exist. It might routinely detect micro black holes. Dont worry these black holes will evaporate and cause no harm.
ALICE - This detector will study a form of matter that existed just after the Big Bang. Yup, the LHC collisions will create conditions that will be close to the original Big Bang that started the whole universe off..
CMS - Also a very cool massive detector like ATLAS. It will look for what causes mass and will also look into the stuff called Dark Matter that apparently makes up a very large percentage of everything.
LHCb - This beauty is looking at Antimatter. Where is the Antimatter ? We dont understand why there is not more of it around, so LHCb is gonna explore this issue.
Soooo.... The LHC is the huge, massive, powerful machine that spins particles around at near light speed and causes them to collide. This will allow us to understand many interesting and potentially important things that could well result in everyday uses and advance mankind to a whole different level of understanding of the universe around us. SoOOoo maybe we might be closer to transporters and warp drive ! hehehe...