In 1905, Albert Einstein enunciated his equation to the world by introducing something new into the whole sphere of physics.
The meaning of the equation is that the energy (E) and the mass (M) are two sides of the same medal, linked by the speed of light (C). Until that time no one thought that this was possible because it was known that they were very different and independent.
Among the many implications of this physical formula, the main consequence is that a mass can release a huge amount of energy: only 1kg mass could energize a nation for a month! The development of the atomic bomb was based on that principle.