to exchange things between something and something else means that something takes in one kind of thing from that something else and expels another kind of thing into that something else
directions_to_get_somewhere is how_to_thing. another_way_to_say_separates_things is divides_objects. thing is substance. separated_thing is divided_thing. thing is attribute. else is river. change is when_one_thing_becomes_another_thing. space is what_between_else. everything is one_thing. otherness is difference.