In Box2dWeb, when we create a body we attach a fixture to the body object. We make the shape, friction, restitution and so on by tinkering with the fixture object.
So from this can we conclude that the fixture is what we really need to tinker with to get the body we want, and the body object we create just an abstract entity? Abstract in the sense that by itself, it is invisible in the canvas after we draw and animate the canvas? The body is just the abstract, formless object that becomes physical once we attach the fixture. Is this right to conclude?