Shapes are defined by their parameters. The simplest shape, the flat Rectangle, is defined by its width and its height. All shapes also have their transformation parameters - these are rotation and translation relative to the world coordinate frame. These can be thought of as three parameters for rotation (three angles about the coordinate axes) and three parameters for translation (x, y and z translation relative to the origin).
A Box shape has three parameters, width, height and depth, and combined with the transformation parameters, it is fully defined by nine parameters. A Truncated Wedge has ten parameters (because it has two ‘widths’ compared to the Box’s one width parameter).
The Shape algorithm uses the edges that are marked on the photos to solve these parameters and rarely do you have to be concerned with them. The Shapes Explorer provides a means of viewing these parameters if you so wish.