This God Particle speech by John Ellis gives an easy-to-digest definition and explanation of the Higgs Boson. With the recent publicity of this seemingly all important particle, John has taken the liberty to fill those interested in just what all the fuss is about.
As John explains, Higgs had a theory that all empty space has matter. The Higgs Boson particle is what makes up this matter. So in other words, the Higgs Boson has the purpose of giving matter to all the other elementary particles.
John adds in his God Particle speech that there are two types of matter that passes through this Higgs field: those that collect matter and interact and those that quickly pass through these spaces as amass-less particles.