Rolle's Theorem states that if a function is continuous on a closed interval [a, b] and differentiable on the open interval (a, b), and if the function has the same value at both endpoints, i.e., f(a) = f(b), then there exists at least one point c in (a, b) where the derivative f'(c) = 0. This means that the function has a horizontal tangent line at that point. In simpler terms, if you draw a smooth curve that starts and ends at the same height, there must be at least one point along the curve where it levels off momentarily. Rolle's Theorem is a fundamental result in calculus and is often used to prove other important theorems, such as the Mean Value Theorem.