In math, pi is a very special number.
Pi is rounded to 3.14.
It's irrational which means it continues on forever so
it's impossible to find all the digits of pi.
For most problems, rounding Pi to 3.14 is acceptable.
For any circle, if we divide the circumference by the diameter, we get pi.
It involves the perimeter or circumference to a circle's diameter.
In fact, this is how the number pi was originally developed and named by the Ancient Greeks, who like Egyptians and Babylonians before them found that dividing the circumference of a circle by it's diameter would always yield the same number, which was approximately equal to 3.14.
It frustrated the Greeks to learn that Pi was a decimal number that had no end because the Greeks believed the circle to be a perfect shape and thus they believed that the ratio of the circumference of a circle to its diameter should yield a more elegant number than 3.14159...