The Fibonacci series was introduced by the Italian mathematician Fibonacci in his book Liber Abaci, where each number is the sum of the two preceding numbers, starting with 1, 1, 2, 3, 5, etc. The Fibonacci series starts with 0 and 1 and each subsequent number is the sum of the first previous numbers. It is used in many fields and can be seen in natural objects like the arrangement of petals and leaves that often follow the Fibonacci sequence of numbers.