The integration of a dedicated physics library to Game Maker: Studio means that you can now take control over all aspects of the physical behaviour of objects within your game world, particularly collisions and object interaction.
The "traditional" collision system (which Game Maker: Studio defaults to) is a "reactive" system, where you check for a collision and then react to that collision with code that you place in individual objects.
These coded "rules" will then govern the way everything in your game world interacts.
In this way, with a few simple code and the correct room setup, you can create very complex interactions between objects and the world which will occur and resolve without you having to code for every single possible outcome.
I was maintaining these in a document on my PC and decided I may as well store them publicly so other people can benefit from what I have learned: Non-kinematic rigid bodies will ignore the hierarchy.When a group of entities are parented together, they form a rigid movement hierarchy family which will move together as if all the entities were one physical object.Each child-entity will follow its parent's movement.If you make one rigid body a child of another and translate the parent. The child’s transform will update so that it remains in place in world space.If you want to couple rigid bodies you need to use joints.