A lighthouse is like a really big flashlight that helps ships know where they are going. It's like a big tower by the water that shines a bright light to help guide boats and ships at night or in cloudy weather. The light is usually very bright and can be seen from far away. The tower also has big stripes on it that help ships know where they're at, like a map. Lighthouses are really important because they help keep ships safe and prevent them from crashing into rocks or other dangerous things in the water.