Critical points are specific values in a function where the derivative is either zero or undefined. These points are important because they can indicate where a function changes direction, such as local maxima or minima. Identifying critical points helps in understanding the overall behavior of the function. In calculus, critical points are often found using the first derivative test. By analyzing these points, one can determine intervals of increase or decrease in the function. This analysis is essential in various fields, including physics, economics, and engineering, where understanding changes in behavior is crucial for decision-making.