Simplify the following text for a Grade 7 native English-speaking person.
Original: Riemann 's explicit formula for the number of primes less than a given number in terms of a sum over the zeros of the Riemann zeta function says that the magnitude of the oscillations of primes around their expected position is controlled by the real parts of the zeros of the zeta function .
Simplified: It is about a special function , the Riemann zeta function .