Fibonacci numbers are a sequence of numbers where each number is the sum of the previous two. It is named after Italian mathematician Leonardo of Pisa, also known as Fibonacci. It is a series of numbers generated by adding the two previous numbers in the series. The first number in the Fibonacci series is 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 and the sequence continues indefinitely. The ratio between any two successive numbers tends to be approximately a constant. The ratio tends to be around 1.618. This ratio is called the golden mean.