Hi,thanks for your answer!
Yeah,it sounds clear.
PolySphere holds the creation information while the shape node holds the actual geometry.
My problem is that I don't understand why the book refers to both nodes as "shapes" and how is it possibile that in edit and query mode the command could access data from the construction node (such as Radius) even using as Name flag the name of the shape node. Maybe is it possible because of the connection between nodes?
And I have another really really silly question: what's the name of a mesh? I mean... in maxscript you can get access to a mesh and all its data using the getnodebyname function or simply with $objectname... and that's it!
Here in maya it seems that this idea simply doesn't work because a mesh is in fact composed by more than one node...so you have to address exactly the one containing the specific info you need.
Sorry again for my very noob questions,but I'd really like to learn deeply, so I think it's better to dig to the foundations