With only m and e changeable the equation doesn't look like much, and on its own it isn't. The only thing this equation tells us is the units energy is measured in. Normally, energy is measured in kg*m^2/s^2. Einstein's equation states that energy(E) is equal to mass(m=kg) times c(the speed of light=m/s) squared(c^2=m^2/s^2). Thus, Einstein and Newton agree with the units energy is measured with, although they state it a little differently.