Imagine you are walking along the integers, one step per number, and you are interested in the distance between primes. If you are standing at a prime number p, then, as a consequence of the Prime Number Theorem, you will expect to walkln (the natural logarithm of p) steps on average before getting to the next prime number. But this is just on average, and sometimes you will have to walk much further, and sometimes much less far. If the Twin Prime Conjecture is true, then there are infinitely many primes such that the next one is just two steps away.