When a shape
can be mapped onto itself by a rotation of less than 360o it is
said to have rotational symmetry.
The flower with 5 petals, for
example, can be rotated about its center to map onto itself through
an angle of 1/5th of a turn and any multiple of this angle, so it
is said to have rotational symmetry of order 5.
The box shaped like
a hexagonal prism, can be rotated about its main
axis through an angle of 1/6th of a turn and any multiple of this
angle, so it has rotational symmetry of order 6 about this axis.
Generally we can make out, an object with rotational symmetry is
an object that looks the same after a certain amount of rotation.