You are likely already familiar with the idea of a slope of a line. If you're not, I encourage you to review it on Khan Academy. But all it is, it's describing the rate of change of a vertical variable with respect to a horizontal variable. So for example, here I have our classic y-axis in the vertical direction and x-axis in the horizontal direction. And if I wanted to figure out the slope of this line, I could pick two points, say that point and that point. I could say, okay, from this point to this point, what is my change in x? Well, my change in x would be this distance right over here.