Blender is an open source, platform-independent 3D modeling tool, which was first released in 1998 as a shareware program. It went open source in 2002. Its features are similar to those in commercial tools such as 3ds Max, Maya, and Cinema4D. However, it has a reputation of having a difficult learning curve compared to other 3D modeling programs. Blender is strongly based on usage of keyboard shortcuts and not menus, which makes it hard for new users to find the options they're looking for. In the last few years, more menu-driven interfaces have been added.
It's not in the scope of this book to teach you everything about the modeling tools that can be used with Papervision3D. This also counts for Blender. There are many resources such as online tutorials and books that cover how to work with Blender.