Answer:
pi [π] is the ratio of a circle's circumference to its diameter, and it is constant [meaning it is always the case] for all circles.
{this is a long number, 3.141592653589793238... is not even the full length, but 3.14 [or 3.14159] is typically used for estimation}
The significance of pi is typically centered in math--it can be used to find values that we don't know of circles. There are other areas of math that have been related back to the value of pi--which is incredible, and genuinely relevant.
We can find pi in the shape of rivers, physics--including waves--DNA
[+ anywhere there is a circle]
hope this helps!! :)