From Academic Kids
A TeV is a teraelectronvolt, i.e., it is 1012 electronvolts, or 1,000,000,000,000 eV. An electronvolt is the amount energy gained or lost by an electron when it is accelerated by the electrical potential of one volt, or 160.22 nanojoules (nJ).
It requires 13.6 eV to remove the electron in a hydrogen atom to infinity.
As explained by Einstein, the eV can be used interchangeably as a unit of energy and mass, and often particles are described as having a mass in eV; for example, an electron has a mass of 0.511 MeV and a proton around 930 MeV.
High-energy particle accelerators use TeV.