This area does not affect gravity/damp. These are generally areas that exist only to detect collisions, and objects entering or exiting them.
This area adds its gravity/damp values to whatever has been calculated so far. This way, many overlapping areas can combine their physics to make interesting effects.
This area adds its gravity/damp values to whatever has been calculated so far. Then stops taking into account the rest of the areas, even the default one.
This area replaces any gravity/damp, even the default one, and stops taking into account the rest of the areas.
This area replaces any gravity/damp calculated so far, but keeps calculating the rest of the areas, down to the default one.