Map and Territory is a motif Wallace uses to highlight the disconnect again between Self and Appearance. He uses the phrase "eliminate the map" in reference to death several times in Infinite Jest.
The ETA boys argue about the difference between "map" and "territory" during a game of Eschaton. Eschaton is a game played on a tennis court that is a little like risk in that territories, controlled by players, are mapped out on the tennis court floor, and old tennis balls are used as nuclear warheads. The game is bounded by a very strict set of rules and boundaries. Once, during a snowy game on Interdepence Day YDAU, tempers flared among the players, and Ingersoll hit Kittenplan in the head with a ball. This, clearly outside of the rules, sparks a frustrated speech from Michael Pemulis, who says:
"Players themselves can't be valid targets. Players aren't inside of the goddamn game. Players are the apparatus of the game. They're part of the map. It's snowing on the players but not on the territory. They're part of the map, not the cluster-fucking territory. You can only launch against the territory. Not against the map. It's like the one ground-rule boundary that keeps Eschaton from degenerating into chaos. Eschaton gentlemen is about logic and axiom and mathematical probity and discipline and verity and order. You do not get points for hitting anybody real. Only the gear that maps what's real" (338).
While this rant is placed within the context of a boy's game, the discrepancy between map and territory is applied to more serious matters throughout Infinite Jest. Self is imperfectly projected out into the world, and if that imperfect image is unsatisfactory to someone, depression or anxiety or worse will ensue. The reconciliation of Self and appearance, of territory and map, is a problem faced by many characters in the novel. As one quick example, Joelle Van Dyne speaks of eliminating her own map during her battle with depression. Joelle's map and the map in Eschaton share the notion of a map veiling the territory: in the Eschaton game, the snow confuses the line between map and territory, making everything “gauzily shrouded” (339), just as Joelle is shrouded in her veil.
According to Wikipedia, "The map is not the territory is a remark by Polish-American scientist and philosopher Alfred Korzybski, encapsulating his view that an abstraction derived from something, or a reaction to it, is not the thing itself, for example, the pain from a stone falling on your foot is not the stone; one's opinion of a politician, favorable or unfavorable, is not that person; a metaphorical representation of a concept is not the concept itself; and so on."
More on Map-Territory Relations