In calculus, a limit is a fundamental concept that describes the behavior of a function as its input approaches a certain value. It helps in understanding how functions behave near specific points, even if they are not defined at those points. Limits are essential for defining derivatives and integrals, which are core components of calculus. Limits can be evaluated using various techniques, such as direct substitution, factoring, or applying special limit laws. They are crucial for analyzing continuous functions and understanding concepts like asymptotes and discontinuities. Mastering limits is a key step in studying more advanced topics in calculus.