What is the Higgs?

image credit CERN
The Higgs boson or Higgs particle is an elementary particle initially theorised in 1964, and tentatively confirmed to exist on 14 March 2013. Peter Higgs from England and Franรงois Englert from Belgium, two theoretical physicists who suggested that an invisible ocean of energy suffusing space is responsible for the mass and diversity of the the universe, were awarded the Nobel Prize in Physics in 2013.
But what exactly is the Higgs?
(thanks Miss Rare)