Prime factorization is essentially the process of breaking a number down by multiplication into all of it's prime factors, the prime numbers that go into the original number evenly.
We can break down 170 into the product 10 · 17. Since 17 is a prime number, we can't break it down any further, but we can express 10 as the product 2 · 5. Since 2 and 5 are both prime, we've broken down 170 into all of its prime components, and we can write its prime factorization as a product of all of these components like this:
170 = 2 · 5 · 17