Gameplay rules are arbitrary rules that are imposed on a gameworld in order to transform the interactions with that world into a gameplaying activity. There are rules, such as having 100 health points, that are abstract and feel at times like an arbitrary imposition. Why is it 100 health and not 200 or 300? We could argue that 100 health points is an abstract representation of the stamina, constitution and vigor of the players character. We could also argue that it is simply an arbitrary way of providing the player with a certain amount of challenge. (as in, if the character had 200 points the game would be much easier).
Rules that are not tightly connected to the pseudo-physical representation of a gameworld are called abstract rules. Examples of these types of rules include the number of lives the player has available as well as those that determine when a game has ended.