Leonardo Pisano, more commonly known as Fibonacci was born in the city state of Pisa. His father was posted as the Pisan trade consul to what is now Algeria. They travelled widely through the Arab world and Leonardo was taught by Arab mathematicians. This allowed him to realise the great advantages that the sophisticated maths used by the Arabs had for both mathematicians and for merchants.
Returning to Pisa in 1200, Fibonacci wrote Liber Abaci. This important work examined many of the problems studied by Arab scholars but it also set out to help merchants and enable them to calculate profits on a transaction. The book was widely copied and imitated as it introduced the Indo-Arab place value number system and the use of Arabic numerals to Europe. He demonstrated the superiority of the Arab system over the Roman numerals and number system used by people like Boethesius.
Fibonacci is also known for his famous sequence of numbers. He himself did not pay great attention to this discovery, but scholars since have found the sequence fruitful and it has been used by many in different areas of maths and science. The numbers came about as a result of asking how many rabbits (in a secluded environment) will be produced in a year from a single pair if it is supposed that each month every pair begets a new pair.
The resulting sequence is 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, … You will notice that each number is the sum of the two preceding numbers. The pattern can be seen throughout mathematics and in nature itself - the daisy for instance often has 34, 55 or 89 petals - all Fibonacci numbers!