So it's the expected value of random variable x minus the expected value of x. You could view this as the population mean of x, times, and then this is random variable y, so times the distance from y to its expected value. Or the population mean. The population mean of y. And if it doesn't make a lot of intuitive sense yet, well one, you can just always kind of think about what it's doing, play around with some numbers here. But the reality is, it's saying how much they vary together. So you always take an x and a y for each of the data points.