For those of you who don't know calculus yet, I encourage you to watch that playlist. But all this is, is saying the area of the curve from here to here. And actually, it turns out for the normal distribution, this isn't an easy thing to evaluate analytically. And so you do it numerically. And you don't have to feel bad about doing it numerically, because, oh, how do I take the integral of this? There's actually functions for it. And you can even approximate it.