A square is
the most symmetric quadrilateral. All its sides are of equal length
and its angles are all right angles. Its diagonals are equal in
length, bisect each other, and cross at right angles. It has 4 lines
of symmetry and rotational symmetry of order 4. Its opposite sides
are parallel.

The square shape is commonly seen as a wall tile,
or paving slab, or as the basic shape in a patchwork quilt, because
it easily tessellates.

Example of a Square: