A Magic Cube is consisted of eight smaller cubes and eight hinges arranged in the three dimensions. In total there are 48 square faces (6 square faces per small cube times 8), 24 of which are visible while the rest 24 are hidden. During folding (or unfolding), visible square faces turn hidden and vice-versa. It measures 9.4 cm x 9.4 cm x 9.4 cm, and uses 424 pieces.
See my other two Magic Cubes here on Rebrickable.