The golden ratio  is a 1.618:1 mathematical ratio, and the number 1.618 is known as phi.  Golden ratios can be found in shells, plants, flowers, and animals, among other places. It is believed to be one of the strongest and oldest connections between math and creative arts.

Putting it as simply as we can (eek!), the Golden Ratio (also known as the Golden Section, Golden Mean, Divine Proportion or Greek letter Phi) exists when a line is divided into two parts and the longer part (a) divided by the smaller part (b) is equal to the sum of (a) + (b) divided by (a), which both equal 1.618.