system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is Pi? Why does it exist? Why was it created? And why is it "infinite"?
gpt
Pi exists because circles exist. Draw a circle of whichever size, measure its circumference, and then divide that value with the length of its diameter. The value so obtained is always a constant (as long as the measurements are accurate) and is called pi. 
Pi is not infinite, because, as said above the ratio of any circle's circumference to its diameter is what is obtained as pi, and is a universal constant.
However, coming to the value of pi, it is true that pi has an infinite number of decimal places. We say that it is an irrational number. For calculation purposes, we use an approximate value of pi, that is 3.14 or 22/7. 
Check out videos of vihart on YouTube on the same.