The Roche Limit is the distance that a moon or satellite can be to a planet before the gravitational tides pull it apart. At the Roche limit the gravitational tides from the planet are balanced by the self gravity of the satellite. At closer distances the satellite is pulled apart. When further away from the Roche limit the satellite can hold itself together under its own gravitational forces.
In this video we balance these two forces and find an expression for the distance at which objects would be pulled apart by the planets tides.
Dr Phil Sutton 