Tessellations are tilings of regular polygons that cover a surface without overlaps or gaps. There are three regular polygons that tessellate on their own: triangles, squares, and hexagons. Semi-regular tessellations use two or more regular polygons, where every vertex has the same configuration of polygons meeting at the corners. Examples of semi-regular tessellations include configurations of triangles and hexagons such as 3,6,3,6 or 3,3,3,3,6.