Leonardo Fibonacci was an Italian mathematician from around 1170-1250 who is known for discovering the Fibonacci sequence of numbers where each number is the sum of the two preceding ones. The sequence begins with 0 and 1 and progresses as 0, 1, 1, 2, 3, 5, 8, 13, etc. with each term defined by the recurrence relation Fn=Fn-1 + Fn-2, where Fn-1 is the previous term and Fn-2 is the one before it.