Right! So if you were to apply this Shader we have described (the blinn or phong with a black color and high reflectivity) to the box (whatever it is you want to act as a mirror), it would have that mirror effect.

For example, create a cube and scale it to resemeble a mirror. Place this shader on said cube, and then place another model (let's use a sphere in this case, just for an example) of some sort in front of it, you would see the sphere model in the mirror cube.