In the formula it is directly relating mas and energy by the ratio of c squared. What does this mean. It means Mass can be converted to energy and vise versa. Also think of this. What happens when something gets faster. You need more energy. So if E goes up and c square remains the same this means that mass goes up. So if you move faster (really fast) your actual mass increases. E=mc^2 also explains why the speed of light is speed barrier because the amount of energy needed to go faster than that speed would require an infinte amount of mass.
