Simpson's Rule is a numerical method used to approximate the definite integral of a function. It works by dividing the area under the curve into an even number of segments, using parabolic arcs to estimate the area of each segment. This approach provides a more accurate approximation than methods like the trapezoidal rule, especially for smooth functions. To apply Simpson's Rule, you need to evaluate the function at equally spaced points. The formula combines the function values at these points, giving more weight to the endpoints and the midpoints. This technique is particularly useful in calculus when exact integration is difficult or impossible.