The Mean Value Theorem states that for a continuous function on a closed interval [a, b] that is differentiable on the open interval (a, b), there exists at least one point c in (a, b) where the instantaneous rate of change (derivative) is equal to the average rate of change over the interval. This theorem is fundamental in connecting the behavior of derivatives to the overall change in function values, providing a formal bridge between local and global properties of functions.