A critical point is an important and special point on a graph of a function. It is associated with a local extremum (maximum or minimum) of the function, either in the x-direction or y-direction. It is also a point on the graph where the derivative of the function is either undefined or zero. In addition, the tangent line of the graph at the critical point is either parallel or perpendicular to the x-axis. Critical points are widely used in mathematics to solve a variety of problems such as solving equations, finding the area under a curve, and determining the global extrema of a function. Knowing the critical points of a function is essential for understanding the behavior of the function and its graph.