The Higgs boson is getting a lot of press since the July 4 CERN announcement that it may have been detected by the Large Hadron Collider, but the boson is only part of the story. See, the real work isn't done by the boson itself, but by the Higgs field, which theoretical physicist Peter Higgs proposed in 1964 as a means of explaining how the Standard Model of quantum physics could explain the mass shown by fundamental particles. The Higgs boson is just a physical manifestation of that field, created when you shove enough energy into it. (In quantum physics, fields and particles are viewed as different ways of representing the same basic physical entity. This is, of course, a bit of an over-simplification, but it's close enough.)
Here is how theoretical physicist Brian Greene explained the Higgs field on the Charlie Rose show on PBS:
Mass is the resistance an object offers to having its speed changed. You take a baseball. When you throw it, your arm feels resistance. A shotput, you feel that resistance. The same way for particles. Where does the resistance come from? And the theory was put forward that perhaps space was filled with an invisible "stuff," an invisible molasses-like "stuff," and when the particles try to move through the molasses, they feel a resistance, a stickiness. It's that stickiness which is where their mass comes from.... That creates the mass....
... it's an elusive invisible stuff. You don't see it. You have to find some way to access it. And the proposal, which now seems to bear fruit, is if you slam protons together, other particles, at very, very high speeds, which is what happens at the Large Hadron Collider... you slam the particles together at very high speeds, you can sometimes jiggle the molasses and sometimes flick out a little speck of the molasses, which would be a Higgs particle. So people have looked for that little speck of a particle and now it looks like it's been found.
Greene isn't the only one out there talking about the Higgs boson, of course. There's also this nice post from Jim Baggott, over at the Huffington Post, which helps to shed some light on why physicists are so excited, and I had an earlier post where I collected together quite a lot of the early explanations that spread across the web in the wake of the LHC announcement.