And the integral sign is literally the sum of all of these rectangles. All of these rectangles for all of the x's between x is equal to 0 and x is equal to 2. But the limit of that as these dx's get smaller and smaller and smaller, get infinitely small, would not being equal to 0, and we have an infinite number of them. That's the whole power of the definite integral. And so you can imagine as these dx's get smaller and smaller and smaller, these rectangles get narrower and narrower and narrower, and we have more of them, we're getting a better and better approximation of the area under the curve until at the limit we are getting the area under the curve. Now we're going to apply that same idea, not to find the area under this curve, but to find the volume if we were to rotate this curve around the x axis. So this is going to stretch our powers of visualization here.