Think of a circular train track, with two engines on. One is going clockwise and the other in the opposite direction. Eventually the trains will collide with each other.

Now "Hadron" (a train) is the name given to a class of sub-atomic particles. Atomic particles, or "atoms" are the things that make up everything you see in the Universe, they can be thought of as building blocks (atomic lego). The sub atomic particles are the sub building blocks of atoms. One such particle is called a "proton" and it's protons that are forced around the track (train-track) to eventually crash into each other.

I suspect you already know what "Large" and "Collider" mean, it's called "Large" because it's bigger than another similar device, and "Collider" because it forces two tiny objects (The so called "Hadrons") to smash in to each other.

Your photo actually shows one of the detectors that sits on the Large Hadron Collider. It picks up the debris that are flown out when the protons collide, and will detect some of the strangest particles that exist.

So in summary, the Large Hadron Collider is the track that the Hadrons move around in. The track is about 27 km long.

However, a more interesting question is "Is its possible discoveries worth the billions it cost to build?"