Tidal locking is a phenomenon where an astronomical body, like a moon or planet, rotates on its axis in the same time it takes to orbit another body. This results in one side always facing the object it orbits, such as the Earth and its moon, Luna. This synchronization occurs due to gravitational forces that create tidal bulges, which over time slow down the rotation of the smaller body until it matches its orbital period. As a result, the same hemisphere of the tidally locked body is perpetually exposed to the larger body, while the opposite side remains in darkness.