The Fibonacci Sequence is the series of numbers. The next number is found by adding up the two numbers before it.

The 2 is found by adding the two numbers before it (1+1)

Similarly, the 3 is found by adding the two numbers before it (1+2),

And the 5 is (2+3),

and so on!
Short Fibonacci Sequence list:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, ...
About Fibonacci The Man
His real name was Leonardo Pisano Bogollo, and he lived between 1170 and 1250 in Italy. "Fibonacci" was his nickname, which roughly means "Son of Bonacci".
As well as being famous for the Fibonacci Sequence, he helped spread HinduArabic Numerals (like our present numbers 0,1,2,3,4,5,6,7,8,9) through Europe in place of Roman Numerals (I, II, III, IV, V, etc). That has saved us all a lot of trouble!
Fibonacci Day
Fibonacci Day is November 23rd, as it has the digits "1, 1, 2, 3" which is part of the sequence (an easy way to remember the sequence). So this November 23rd 2015 let everyone know!