A fault is a crack or fracture in the Earth's crust where rocks on either side have moved. This movement can happen slowly over time or suddenly during an earthquake. Faults are important because they can help scientists understand how the Earth’s surface changes and can also indicate where earthquakes might occur. There are different types of faults, such as normal faults, reverse faults, and strike-slip faults. Each type has a unique way of moving. For example, in a normal fault, the ground above the fault moves down relative to the ground below. Understanding these faults helps us prepare for natural disasters and protect communities.