The Standard Model of Physics neatly organizes matter into building blocks and forces. The building blocks are called the fundamental particles and the forces are called fundamental forces.
The standard model describes nuclear interactions between subatomic particles, but does not give up a whole explanation of those fundamental interactions. This model has been jokingly called "the theory of almost everything".
If one last particle, the Higgs Boson, could be created and observed, then the Standard Model of Physics would gain status as a strong unifying theory.
The model describes 12 elementary particles of spin, called Fermions, and classifies electromagnetic functions as strong, weak and electromagnetic. The force carrier particles that mediate the dynamics of subatomic particles are called gauge bosons.
The Higgs boson is both a gauge boson and a force carrier.
The Higgs boson is part of an invisible energy field called the Higgs Field. This energy field is believed to stretch throughout the universe where it clings to particles, dragging them along and giving them what humans conceive of as "mass". The Higgs Boson is believed to have been created shortly after the big bang. Most particles react to it and are given their mass.
Peter Higgs is is Edinburgh University physicist for whom the particle is named. Higgs, Robert Brout, Francois Eglert, Gerald Guralnik, C.R. Hagen and Tom Kibble developed the theoretical basis for the existence of the Higgs Boson in the 1960s.
The Higgs boson is called the "God" particle simply because, while it is predicted by standard model, it is the only fundamental particle from the Standard Model that has never been observed. The Guardian recounts a story that that physicist Leon Lederman wanted to name the particle that "goddamn particle" but his editor would not allow it.
Higgs himself did not like the term "God Particle" because of of the potential for offense.
The only way that a Higgs boson could ever be observed is after particles have been smashed at the subatomic level with enough energy to recreate the conditions that went on during and after the "big bang". The only machine that has been capable of producing such energy is the Large Hadrion Collider at the European Particle Laboratory in Cern.
The search for the Higgs Boson went on in the mass ranges where scientists expected it to be. If the particle was not found in one mass range, the scientists exclude the particle from that mass range and moved on to another. After August 2011, the possible masses for the Higgs were excluded at 95% confidence level.
In December, 2011, scientists found the most compelling evidence so far that the Higgs Boson resides somewhere around the 124GeV mass range. While the proof was not compelling enough for a definite find, there is a lot of excitement.
CERN director general Rolf Heuer predicted that 2012 will be the year of the Standard Model Higgs boson. The particle will be either observed or it will be excluded in all mass ranges. If the Higgs boson is excluded in all mass ranges, then the Standard Model will not be completely vindicated.