Energy=mass times light speed squared, it can be interpreted in different ways like some ppl say we can derive this to mass equals energy over light speed squared ( m=E/c^2)which shows that we r all energies. The formula was written this way at first btw Also, some scientists say we change to energies if we travel in light speed gn we cant travel in light speed cuz we aint photons😅 What Einstein actually wrote is a little different. He suggested and proved that motion or speed contributes to a mass of smtn ena scientists, mass sayhon milut mass at rest new. In this case, this formula basically means something would weigh heavier if it were in motion because it has more energy, which is the additional kinetic ENERGY caused by its motion. If there are two objects with the same rest mass, the one travelling faster would be heavier. Mass is not only the amount of matter but also the energy it posseses. So Actual mass = amount of matter + E/c^2, Mejemerya Einstein M=E/c^2 blo neber yetsafew, gn other scientists changed the position to understand energy n make nuclear weapons with the vast amount of energy this formula can generate. I think google explains it better than me so i think u should google it, many scientists misunderstood it n gave their own assumptions which mislead a lot of other sceintists. Some said we can creat mass(particles) out of energy which is logical but Einstein never said that.