Minimum safe altitude is the lowest height or altitude a plane should fly above the ground to prevent crashes and accidents. It is like when you are told to stay away from a hot stove because you might burn yourself. In the same way, pilots are told to fly above a certain height to keep safe from things on the ground that may harm the plane. Just like how it is important to listen to your parents when they tell you what to do, pilots have to follow the rules made by the aviation authorities and fly at the minimum safe altitude to keep everyone safe.