The rate of change is a fundamental concept in mathematics and physics that describes how a quantity changes in relation to another quantity. It's essentially the speed at which something is changing. For example, the rate of change of position with respect to time is velocity, and the rate of change of velocity with respect to time is acceleration.
In simpler terms, if you have two points on a graph, the rate of change between them is the "steepness" of the line connecting those two points. It's calculated as the change in the dependent variable (usually 'y') divided by the change in the independent variable (usually 'x'). The formula for the average rate of change between two points $(x_1, y_1)$ and $(x_2, y_2)$ is: