Why is it called the Higgs? It was named for Peter Higgs (see video above), a theoretical physicist now retired from the faculty of the University of Edinburgh, who predicted its existence. Around the same time, two other physicists, François Englert of the Free University of Brussels and Tom Kibble of Imperial College London, independently came to a similar conclusion. Had the last of these published first, we might now be celebrating the discovery of the Kibble boson.
So, what is a theoretical physicist? A theoretical physicist is someone who, using mathematics, tries to find solutions to as yet unexplained issues in physics. An experimental physicist tests these solutions in experiments using equipment such as the enormous CERN Large Hadron Collider in which the Higgs Boson has evidently now been found. Richard Feynman, one of the great theoretical physicists of the last century, who played an important role in defining what physicists call the "Standard Model" in which the Higgs plays a vital role, once described the difference by recalling a talk he gave to some experimental physicists at the Lawrence Livermore Laboratory in California. Referring to a recently discovered particle, he said, "Let's suppose its spin [a quality all particles have, which can always be expressed as an integer or an integer plus one half] is two and a half." A voice with a heavy Brooklyn accent called out from the audience, "Hey! It ain't two and a half, it's tree. Dey measured it."
This isn't to say that experimental physicists are all down-to-earth types; far from it. The Guardian's Sample describes Fabiola Gianotti, a leader of the CERN team that may have discovered the Higgs, as having "an education steeped in ancient Greek, philosophy and the history of art--she had also trained as a pianist at the Milan conservatory." Sample also quotes her as saying: "physics is art, aesthetics, beauty and symmetry."