The Mean Value Theorem states that for a continuous function on a closed interval, if the function is also differentiable on the open interval, there exists at least one point where the instantaneous rate of change (the derivative) equals the average rate of change over that interval. This means that there is at least one point where the slope of the tangent line is the same as the slope of the secant line connecting the endpoints of the interval. In simpler terms, if you draw a straight line between two points on a curve, the Mean Value Theorem guarantees that there is at least one point on the curve where the slope of the curve matches the slope of that straight line. This theorem is fundamental in calculus and helps in understanding the behavior of functions.