Why does a regular octagon doesn't tesselate?

A regular octagon does not tessellate because the interior angles of a regular octagon, which measure 135 degrees, cannot perfectly fit together without leaving gaps. When attempting to tile a plane with regular octagons, the angles do not sum to 360 degrees around a point, making it impossible to cover a surface without overlaps or spaces. In contrast, shapes like equilateral triangles, squares, and hexagons can tessellate since their angles can combine to meet the necessary conditions for tiling.