The G-MUNU represents the curvature of space-type, and the T-MUNU represents the distribution of matter in the universe. The bit in the middle is constant, so we can take it out and we are left with this beautiful relationship. curvature is proportional to matter distribution. The equation and general relativity as a whole was summarised in this way by physicist John Wheeler. Space-time tells matter how to move, matter tells space-time how to curve. Einstein's equation represents half of modern physics, and thus is where we shall leave relativity for now.