A Tessellation (or Tiling) is when you cover a surface with a pattern of flat shapes so that there are no overlaps or gaps.
A regular tessellation is a pattern made by repeating a regular polygon.
There are only 3 regular tessellations:
Triangles Squares Hexagons 3.3.3.3.3.34.4.4.46.6.6
A vertex is just a "corner point".
What shapes meet here?Three hexagons meet at this vertex,
and a hexagon has 6 sides.So this is called a "6.6.6" tessellation.
