It shows up in nature all of the time. And if people are trying to kind of, if you do take data points from something that is very, very complex, and that it is the sum of arguably many, many, almost infinite individual independent trials, it's a pretty good assumption to assume the normal distribution. We'll do other videos where we talk about when it is a good assumption and when it isn't a good assumption. But anyway, just to digest this a little bit, and let me actually rewrite it. This is what you'll see on Wikipedia, but this could be rewritten as 1 over sigma times the square root of 2 pi times, exp is just e to that power, so it's just e to this whole thing over here, minus x minus the mean squared over 2 sigma squared. This is a standard deviation. Standard deviation squared is just the variance.