The symmetry design means a mirror image as one side is the mirror image of the other. Symmetry can occur in any orientation as long as the image is the same on either side of the central axis.
This type of image has great appeal — it makes for “good” shape relationship. Many people automatically gravitate to symmetry. We are symmetrical after all — two eyes, two ears, etc.. Look around at consumer products and graphics (printed materials) to see how many use symmetry. You will find that it is the dominant organizational concept.
The symmetry creates balance, and balance in design creates harmony, order, and aesthetically pleasing results. It is found everywhere in nature, and is probably why we find it to be so beautiful
There are three types of symmetry: reflection (bilateral), rotational (radial), and translational symmetry. Each can be used in design to create strong points of interest and visual stability.