The "Epsilon-delta" definition is a formal way to describe the concept of limits in calculus. It provides a precise method to show that a function approaches a specific value as the input gets closer to a certain point. Here, "epsilon" (ε) represents how close we want the function's value to be to the limit, while "delta" (δ) indicates how close the input must be to the point of interest. In this framework, for every ε greater than zero, there exists a δ greater than zero such that if the distance between the input and the point is less than δ, the distance between the function's value and the limit is less than ε. This rigorous approach is essential for understanding continuity and differentiability in mathematics.