The Fibonacci sequence is an integer sequence where each number is the sum of the two preceding ones, starting from 0 and 1. It was invented by Leonardo Fibonacci in his book Liber Abaci in 1202. The sequence is closely related to the golden ratio and appears throughout nature in patterns of spirals in shells, flowers, pinecones, and galaxies. It has also been used in art, architecture, and mathematics due to its aesthetic appeal from approximating the golden ratio.