This document provides an introduction to calculus and functions. It discusses that calculus originated in the 17th century through the work of Newton and Leibniz. A function is defined as a relationship between variables where each value of one variable corresponds to a unique value of the other. Functions can relate multiple variables as well. Examples of functions include the area of a circle as a function of its radius and the perimeter of a rectangle as a function of its length. The document provides exercises on evaluating functions and relating composite functions.