Gravity bombs, also known as free-fall bombs, are explosive devices that rely on gravity to reach their target. They are typically dropped from aircraft and do not have any propulsion system of their own. Instead, they fall towards the ground, gaining speed due to gravity until they impact the target. These bombs can vary in size and explosive power, and they are often designed to penetrate structures before detonating. Common types include general-purpose bombs and penetrator bombs, which are used in military operations to destroy enemy fortifications or vehicles.