A concave polygon is a type of polygon that has at least one interior angle greater than 180 degrees. This means that at least one of its vertices points inward, creating a "caved-in" appearance. Unlike convex polygons, where all interior angles are less than 180 degrees, concave polygons can have various shapes and sizes. Examples of concave polygons include shapes like a star or a crescent moon. The presence of an inward-pointing vertex distinguishes them from other polygons, such as convex polygons, which maintain a more outward shape. Understanding concave polygons is essential in geometry and design.