The calculus pages are highly experimental. Volunteer high school students are needed to read through the set of pages and comment as to which portions could benefit from better explanations. Differentiation determines the slope of a function. Differentiation converts position to velocity. Differentiation converts velocity to acceleration.
Integration determines the area under a function.
Integration converts acceleration to velocity. Integration converts velocity to position. A spacecraft accelerates and we can monitor the force applied by the engines as a function of time. We haven't discussed how to differentiate or integrate yet. The C is a constant that we will talk about later.