what does the unit MeV/c2 means

MeV/c² is a unit of mass, specifically the mass-energy equivalence in particle physics. It stands for "mega electron-volts per square of the speed of light". It is used to measure the mass of subatomic particles or the energy of photons. The speed of light is squared because of the famous equation E=mc², which relates energy and mass. One atomic mass unit (amu) is approximately 931 MeV/c².