The generated API documentation for 1.8.1 is not correct. I suggest looking at the documentation for the latest version instead, I think it’s a bit clearer: panda3d.org/reference/devel … /annotated
I’ll explain why there are two package trees, “panda3d” and “direct”. “panda3d” contains the core of the engine (panda3d.core) and all modules that have been implemented in C++. The “direct” tree is a Python package tree containing higher-level classes that were implemented in Python, such as Actor, which lives in the module direct.actor.Actor.