Today I just experimented exporting some models with XSIZETools, but sometimes, when I do it, i get a notification saying ">Some part of the Model< missing primitive type name (cube, cyl, sphere).

Can somebody explain me what it means? And specially, does it hurt anything?

P.S. Sorry if this is a noob question, but as mentioned, today was my first day dealing with this kind of stuff.

It doesn't hurt anything. primitive type name is quite simple. your model isn't named with a primitive name e.g. cube, cyl, sphere.