What is the main difference between the 2D Physics System

I’m looking at the features, while there was a lot of examples for 3D projects.
The 2D examples were less.
I’m looking on how can I port my Unity games to Cocos creator.
But one of my confusions are this for now. What is the difference here?
Builtin 2D physics is Chipmunk ?


Builtin 2d physics is just collision detection, no engine used.
We only use Box2d as full featured physics engine for 2D
You can try the demo here