This is a simplified rehash of Vincent's old cloud-n-box posts. I'm just repeating it to myself, with different pictures. Also, I noticed lots of people were confused by Vincent's illustrations so maybe this will be more clear to some if there's anyone still having trouble with those.
Here we have a bunch of people sitting together around a table playing a game. They're imagining stuff that's happening in the game world. The rules say something like: "Halflings get a +2 Dodge bonus against enemies that are larger than man-sized.". In the game world, the halfling hero is fighting an ogre. The player(s) need to judge [lightning bolts] the fiction, the imaginary (non-tangible) content to see if this rule applies. (In the picture in their heads) the ogre is larger than man-sized, so it does. The halfling gets a +2 bonus to his dice (the tangible).
Here the reverse is happening. The rules say something like "If you roll equal or higher on your attack roll, you hit the enemy." So the player(s) need to judge the dice to see if they hit or not. And then interpret that information to adjust the imaginary picture in their heads.
So the entirety of play can be summed up as this: through the player, by mediation of the rules, the dice (numbers, character sheets, counters, cards...the tangible, mechanical, non-fictional) and the imaginary pictures of what's going on influence and interact with each other.
Part 2 coming up.