Calculus is useful math. Useful for physics, chemistry, biology, business and all kinds of other areas. You need calculus in order to do quantitative analysis of how variables change over time (derivatives) or sum up all kinds of contributions that add up to a total (integration).
We will begin our study of the subject by a review of basic math, which we will be necessary throughout our study of this material. Then we will look into the concept of a limit $\lim$, which is pretty much the only new mathematical concept that will be required.
Starting with limits, we can define the concept of derivatives ($f'(x)=\frac{df}{dx}=\lim_{\Delta x \to 0} \frac{\Delta f}{\Delta x}$) and integrals ($\int_a^b f(x) dx$).