Prime numbers are unique. Unlike all other numbers, prime numbers cannot be divided equally by a whole number to get a whole number result except for itself and the number 1.
By contrast, every other number but prime numbers will include other numbers as factors. Also called composite numbers, when you drill down far enough, you'll find each has a unique factorization made up of nothing but prime numbers.
If you start counting up from 1, you'll frequently run into prime numbers at the beginning. But as you count higher and higher, you'll find prime numbers become fewer and farther apart. At first glance, it seems like they're randomly distributed among all the numbers you're counting. But that appearance is deceptive, because when you tease the numbers just right, a non-random pattern emerges.
The following video by Physics Explained's Rhett Allain is one of the best we've seen in establishing the foundation of just how the numbers have to be teased to reveal the pattern that the prime numbers are following.
In the video, New Scientist's Jacklin Kwan focuses on the Riemann Hypothesis, which describes the pattern that prime numbers appear to follow into infinity, which is the biggest unproven conjecture in math: