AxoTools is not a 3D application, but tries to assist illustrators in achieving a 3D look the best it can. Simple shapes are pretty straightforward, but complicated shapes can wind over and under each other like an Escher drawing. In that case, AxoTools evaluates the paths and makes its best guess on correctly stacking the pieces.
When a path is extruded, AxoTools creates closed paths for fillable areas and open paths of multiple stroke weights. To make things more easily edited, the pieces are organized into groups. In the Layers panel, you can expand these groups to find the pieces you may want to edit. Compound paths contain elements nested inside of other elements, so things get a bit more complex.
The front surface is named as a “cap,” and is placed above all of the edge pieces. The edges, which give it depth, are divided into surfaces. Each surface is composed of fillable “panels,” stroked “paths” that follow the original path’s shape, and “connector” pieces for corners that connect the front cap to the rear cap (the rear cap and hidden surfaces may or may not be drawn depending on your Extrude panel settings).