Mean Motion Resonance occurs when two orbiting bodies, like moons or planets, exert regular, periodic gravitational influence on each other due to their orbital periods being related by a ratio of small integers. This relationship can lead to increased stability in their orbits or cause significant changes over time. For example, the moons of Jupiter, such as Io, Europa, and Ganymede, are in a 4:2:1 resonance. This means that for every four orbits of Io, Europa completes two orbits, and Ganymede completes one. This gravitational interaction helps maintain their orbits and affects their geological activity.