THE BASICS OF TESSELLATION
So what shapes will tessellate? There are only 3 regular geometric shapes that can. 'Regular' means that all sides are equal, and internal angles are equal. The 3 regular geometric shapes that tessellate are the equilateral triangle, square and hexagon.
In the picture on this page, the 'F's show that the shapes can be flipped and rotated without affecting the shapes' ability to tessellate. This can make whole pictures more varied and interesting. Not all the possibilities are shown here.