When two bodies collide or slide against each other, dynamic friction creates a decelerating force. The force is in the opposite direction to motion along the plane of contact. It is proportional to the product of the coefficient and the component of force that is pushing the bodies together (e.g., the weight of an object on a sloping surface).
When two bodies interact, the coefficient of dynamic friction for their interaction is the product of their respective DynamicFriction values. The coefficient of dynamic friction of obstacles is set in the Simulate Rigid Bodies node.