Null is basically an element that isn't listed in the list of elements in the code.


Take for example, Pokemon Blue/Red. The variable for pokemon identity went all the way to 255, but there were only barely half as many actual pokemon in the game itself.

....So what were all the other empty spaces? Unintelligible nonsense pokemon made of glitchy tiles and sounds and moves, their attributes gathered from areas of the game's ROM that were packed into the spaces to save space since the rom's size was relatively small.

Null element is essentially that, depending on its identity (as in there's quite a few of them) it can have entirely different properties, which depend even further on the numbers being stored in memory where it happens to look for the non-existent element.