LHC Q&A, page 1

Originally posted by Alora
what, exactly, is the main goal of this project in your own words ?

Hmmm... I'll try and make it as general as possible:

Matter is by far the most interesting subject of study in the natural sciences, because, unlike say energy and spacetime, it has structure. To date, all experiments suggest that all characteristics of material objects can be understood by understanding how the basic constituents of an object function. To paraphrase the saying, it seems that matter is precisely the sum of its parts, and no more. Thus, the study of these constituents, the elementary particles, called particle physics, is the most important foundation block of all natural science.

Now, study of elementary particles requires high energies, for three principal reasons:

At terrestrial conditions, matter mostly occurs in the form of molecules, which are annoyingly complex objects. But, as well all know from everyday experience, we can break objects into fragments by smashing them together. Smash two molecules together with sufficient energy, they break down into atoms. More energy, the electrons come off and we get to see the stripped nucleus. More energy, the nucleus disintegrates into protons and neutrons.
Now, it turns out that by increasing the energy further, we don't manage to break up protons. But, eventually, we observe something that we're not familiar with from everyday experience, namely that if we smash hard enough, things come out of the collision that didn't go in. Basically, this would be equivalent to crashing two cars into each other with enough speed, resulting in two crunched-up cars and two motorcycles. The reason this happens is that at a microscopic scale, energy and matter can be converted back and forth, famously expressed as E=mc^2. So, by smashing two protons into each other hard enough, you can end up with two protons and one (or many) extra particle pairs. These particle pairs occasionally turn out to be things that we don't ordinarily find in nature. By observing these, we can build a more comprehensive theory of elementary particles and their interactions than based on observing just naturally occuring ones. One of the things that people are excited about when it comes to LHC is that for the first time, the collisions will be energetic enough to produce the predicted Higgs-particle.
The last aspect is much less tangible than the two previous ones, but is also the most fascinating for many. At everyday energies, we observe four forces which all behave quite differently: Gravity, electromagnetism, and two nuclear forces that have no large-scale effects. The way in which particles react to these forces depends on their charges. The electrical charge is well-known, the two nuclear forces have similar charges (one of them is called "colour charge", because whereas the electrical charge has two aspects, labelled positive and negative, this one seems to have three, labelled "red", "green" and "blue". Mass can be thought of as a particle's gravitational charge.
The fascinating thing is that the forces suddenly begin to exhibit parallels and eventually become indistinguishable from one another as the particles subject to them become more energetic. As it is assumed that the universe was initially at a high-energy state, from which it expanded and "cooled down" to its current state, it follows that in this initial state there was just one unified force. As certain threshold energy levels were reached, the forces separated one after the other in a process called "symmetry breaking". It is thought likely that once we manage to recreate and fully understand this process, we will have a much better handle on not only particle physics but also many cosmological puzzles which stem from this early period of the universe.

Sorry, didn't mean for this to get this long, hit the character limit again.