The document discusses two methods for determining prime numbers: the Sieve of Eratosthenes and the Sieve of Atkin. The Sieve of Eratosthenes involves listing all numbers from 1 to 100, crossing out numbers that are not prime like multiples of 2 and 3, and the remaining numbers are prime. The Sieve of Atkin is a newer and faster method that is based on the Sieve of Eratosthenes but used in algorithms due to being tedious to do by hand.