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 "cave-like" indentation. Unlike convex polygons, where all interior angles are less than 180 degrees, concave polygons can appear to have a notch or a dip. Examples of concave polygons include shapes like a star or a crescent moon. These shapes can have various numbers of sides, such as quadrilaterals or hexagons. Understanding concave polygons is important in geometry, as they help illustrate the diversity of polygonal shapes.