What does the equation ?E? = ?mc?2 mean?

Solution 44E The principle of equivalence of mass and energy states that the mass and energy are equivalent. Which means, if anything has mass, the object will have the equivalent of energy and vice versa. The relationship between mass and energy is given by the famous formula of Einstein, which is written as Where E is the equivalent energy, m is the equivalent mass and c is the speed of light in vacuum. So the above formula states that it is possible to convert mass into energy or vice versa. If we convert m mass into energy the amount of energy will be , or if we convert E amount of energy into mass, the amount of mass will be .