Tessellations are different from patterns in that patterns usually
do not have distinct closed shapes. A closed shape is a shape
that has a definite interior (inside) and definite exterior (outside).
The wide variety of tessellations can be categorized based on
whether they are composed of polygons. (Polygons have the requirement
that its boundaries must be straight lines.) The section of this
site labeled "Mosaics/Tilings" deals exclusively with tessellations
There is a class of techniques used to create tessellations of
shapes that represent actual objects; these tessellations are
not necessarily composed of polygons. Notably, the famous Dutch
artist M.C. Escher used this class of techniques to create many
of his famous works of art. The section of this site labeled "Escher"
deals exclusively with this class of techniques.