It was actually Gauss who came up with it. I think he was studying astronomical phenomenon when he did. But it's a probability density function, just like we studied the Poisson distribution. It's just like that. And just to give you the preview, it looks like this. The probability of getting any x, and it's a class of probability distribution functions. Just like the binomial distribution is and the Poisson distribution is, based on a bunch of parameters.