Let's say someone wanted to find the derivative with respect to x of the integral from, I don't know, I'll pick some random number here. So pi to x of, I'll put something crazy here, cosine squared of t over the natural log of t minus the square root of t dt. So they want you to take the derivative with respect to x of this crazy thing. Remember, this thing in the parentheses is a function of x. It's value. It's going to have a value that is dependent on x. You give it a different x, it's going to have a different value.