Effectors
Imagine our hero is crossing an enchanted room, so he starts to float due a powerful spell. In this case, while the hero is within this room, gravity should be contrasted by a (magical) force. As a result, we need to specify that in that room, there is a force that makes our hero levitate.
Similarly, imagine the hero drops a box in a lake. The box doesn't sink at the same velocity as it falls; moreover, it might float. Therefore, in our game, we need to specify that the region delimited by the lake has special physical properties.
In Unity, this can be achieved by using effectors. Effectors are some components that affect the behaviour of rigidbodies in certain region of the game world. They are really different from each other, because they do different things, although the core concept is the same: they...