Once the dynamics world has been created, you can create rigid bodies into the world.
A rigid body represents an object that you want to simulate in the world. It has a mass, a position, an orientation, a type, and one or several collision shapes. You can also create joints between the bodies in the world.
The dynamics world will compute collisions between the bodies and will update the bodies position and orientation accordingly every time step.
In ReactPhysics3D, the RigidBody class (which inherits from the CollisionBody class) is used to describe a rigid body.
r3d.Body:applyForce applies a force to this body