Who can tell me the history behind Pi? Please?

Jimmy has 24 apples but only needs 542 of them the rest he decapitates because they are stupid but anyway he eat 157,986 of them green apples and throws out 2 of the purple apples then how many of the red apples does he have if he ate 43 blue apples to make apple pie? 

He ate the e so now there is 3.141592653 black apples on the toilet seat.

The number π is a mathematical constant, the ratio of a circle's circumference to its diameter, commonly approximated as 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, though it is also sometimes spelled out as "pi"