Zeroes and prime numbers ascend in the mist at Zeta Valley | Science News | Scoop.it
A prime number can only be divided by itself or 1, such as 2, 3, 5, 7, 11, 13, 17...and so on. The curve simply represents the number of prime numbers below a certain x. So when x=100 then the number of primes below 100 is 25, and if x=1000, the count is 168. Here are some more values of (x), as the y-axis counter is known (not related to Pi, the ratio between the circumference and diameter of a circle)

In his famous essay, "The First 50 Million Prime Numbers", Don Zagier writes: "For me, the smoothness with which this curve climbs is one of the most astonishing facts in mathematics."