panda3d.core is a package that exposes many (most but not all) Panda3D C++ classes and functions to Python. It’s named ‘core’ because it is the core of Panda3D, the are classes in that package like NodePath, PandaNode, Filename, CollisionNode, Camera, ShaderGenerator, Texture and many, many, many more (full list here: panda3d.org/reference/1.9.0/ … nda3d.core).
There are other packages like panda3d.bullet or panda3d.ai, there’s also ‘direct’ (not panda3d.direct, just ‘direct’) that has all the modules implemented in pure (?) Python like ShowBase or DirectObject.
Many people (like Yours Truly) just write from panda3d.core import * at the top of every script and just use the Panda3D modules without thinking much where they come from.