Fault

Example:

Imagine walking on a sidewalk when you suddenly come across a crack where the two sides have shifted slightly apart. Just like this crack disrupts the smooth path you intended to walk on, a fault is a break in Earth's crust where sections of rock have moved relative to each other. In both cases, the crack represents a division where shifts have occurred—on the sidewalk, it's the concrete slabs moving apart, while in Earth's crust, it's the movement of rocks along the fault line.