Limits are a fundamental concept in calculus that describe the behavior of a function as its input approaches a certain value. They provide a precise way to understand the behavior of a function as it approaches a particular value, and they are used to define derivatives and integrals. The limit of a function is the value that the function approaches as its input approaches a particular value. In some cases, the limit of a function may be finite, and in others it may be infinite. Limits are used to analyze the behavior of functions near specific points, such as their behavior at infinity, and to understand the behavior of the derivatives and integrals of these functions. By understanding limits, one can better understand the behavior of functions and use calculus to analyze and model real-world phenomena.