The Moon is tidally locked to the Earth. When two rotating bodies orbit each other, they raise tides in each other. These tides cause mechanical friction. So tidal activity absorbs a lot of energy out of the rotational energy of the bodies. In other words, the energy in the form of rotational inertia is partially converted into tidal, geophysical changes in the bodies involved. The Moon's rotational inertia has been exhausted, converted into geophysical change in the Earth and Moon. The Moon, being much smaller than the Earth, long ago dissipated enough energy to lose rotation so that its tidal bulges are now always aligned with the gravitational pull of the Earth. The Earth still raises a "tide" in the Moon but it is in a balanced, steady state now and does not stretch the rock any more -- there's no more spin for the Moon to give up.