The picture attempts to show the region given by the constraints z \geq 0, y \leq 4, z \leq x^2 and y \geq x^2.
Note that z=0 is the xy-plane underneath the figure, y=4 is the plane on the right hand vertical face of the box. The region is under the parabolic cylinder z \leq x^2 and to the right of the parabolic cylinder y \geq x^2. The region actually has two components split by the parabolic cylinder z \leq x^2.