Only three regular polygons can tessellate the plane: triangles, squares, and hexagons. A tessellation is formed by arranging identical regular polygons edge-to-edge without overlaps or gaps. Triangles and hexagons tessellate by sliding or gliding the shapes, while squares tessellate by directly lining up under each other. The document provides examples of tessellations made of triangles, squares, and hexagons to illustrate these concepts.