Question

my question is e=mc2 what the mean

Answer 1

E=mc^2 is Einstein mass energy equivalence equation
This equation depicts that mass +energy of universe is conserved

If there is an decrease in mass of universe at same time equivalent amount of energy is produced

E.g. sun

Answer 2

Here E means the energy, m means mass and c means the velocity of light.
This is the equation of Einstein.
Here it refers that, if a particle moves as same velocity as light it will be transfer in energy .