What does this Python code do?
```
import random


def montecarloPi(calcs):
    hits = 0

    for i in range(calcs):
        x = random.random()
        y = random.random()
        if (x**2 + y**2) < 1:
            hits = hits + 1

    return 4.0 * hits / calcs


print(montecarloPi(10000))
```
This code estimates the number pi using the Monte Carlo method (that is, by generating a large amount of random numbers and doing things to them to get results).

To be more specific, the code generates two random numbers x and y, from 0 to 1 each. Those numbers will then implicitly be treated as coordinates of a point. It then measures the square of the distance between point (x,y) and point (0,0); it does so by squaring x and y and summing the squares. Next, it checks if this squared distance is less than 1 and thus, if the non-squared distance is less than the square root of 1, or simply 1. In other words, the code checks if this point lies inside a circle of radius 1 and origin (0,0).

The code does the above 10 000 times, as defined by the last line of the code. 

The probability of a single iteration of the above method resulting in a hit (in a point hitting the inside of the circle) is pi/4 - that's because the points can land anywhere in a square of side 1, but it only counts in the area where this square overlaps with a circle - this area happens to be a quartercircle. The probability is thus equal to (area of the quartercircle)/(area of the square) = (pi * 1^2 /4) / 1 = pi / 4.

While randomness will never be fully predictable, we can be statistically sure that given enough trials (10 000, as mentioned), the ratio of the number of hits to the total number of trials will be close to the above probability. Thus, the code takes this ratio and multiplies it by 4 to extract an approximation of pi from an approximation of this pi / 4 fraction.

The code then prints out the result (the number pi).
Ok, so what is the number pi?
Pi is a mathematical constant that represents the ratio of the circumference of a circle to its diameter. It is an irrational number, which means it cannot be expressed as a finite decimal or fraction, and its decimal representation goes on forever without repeating. The value of pi is approximately 3.14159, but its decimal representation extends infinitely. The Monte Carlo method used in the code you provided is one way to estimate the value of pi.