Without the figure, I'm making the following assumptions:
- Points P and Q are on adjacent sides, not opposite sides
- The "shaded area" is the square made by connecting point P to the center of the original square, then connecting the center to point Q
Let's call the length of each side of the original square a. The original square would have an area of a·a = a2. Since points P and Q are midpoints, the shaded square would have sides = 1/2 of the sides of the original square, or a/2. The area of the shaded region would be (a/2)·(a/2) = a2/4. Hence it has 1/4 of the area of the original square.