I can't find anything in the help.
hmmm ok, thank you for the fast reply. I was thinking they were some kind of "solids". In AutoCAD you have both kinds of primitives: surfaces and solids; whereas here in Maya you have only surfaces. I'm just starting with Maya and it's modelling process is very different than autocad. I feel I don't have any precision! Thank you Luismg
AutoCAD is used mostly for building 3D representations of actual products to be made, so they've made more of an effort for exact measurements. Maya isn't used for that sort of thing as often. There are measuring tools though.