There are two types of symmetry that you should know:


Reflectional Symmetry 
Rotational Symmetry 
 A figure has reflectional symmetry or symmetry about a line if reflection across the line produces an identical figure.
 A figure has rotational symmetry or symmetry about a point P is a rotation of k degrees, 0<k<360, clockwise or counterclockwise, about P produces an identical figure.
Note that the figure on the left does not have symmetry about a point, and
the figure on the right does not have symmetry about a line. Many of figures, however, have both types of symmetry.