why does pi =3.14

pi is circumference divided by the diameter.

difference implies subtract, which is not correct.

because pi actually is irrational and has an infinite amount of digits (or so we think) so we shorten it to the first three because usually you dont have to get too specific with circles. but when you do, um, itll be like actual pi or whatever

$${\mathtt{\pi}} = {\mathtt{3.141\: \!592\: \!653\: \!589\: \!793\: \!2}}$$

except it doesnt just end there it keeps going

To expand on jony's answer, pi is the difference between diameter and the circumference of a circle