In Universe Sandbox ² Alpha 19, you can see these effects when a satellite tightly orbits its primary body, or when a star gets too close to a massive black hole, or even if two identically-sized bodies are in a close binary orbit. Outside of the Roche limit, these tidal forces are still present and can heat bodies in close orbits.
Essentially, the gravitational force acting on the closer side of the smaller body is stronger than the force acting on the far side. When a small celestial body approaches a larger body at a distance inside its Roche limit, it begins to stretch and disintegrate due to tidal forces. In this simulation, the Moon is orbiting Earth within the Roche limit and is being torn apart by tidal forces.
