Editing Magic: The Gathering Gameplay Principles (section)

===Quadrant theory===
Quadrant theory is very useful in Limited because of the importance of the board state. Quadrant theory should be on a player’s mind both during drafting (assuming the player is playing some sort of draft) and deck construction (assuming the player is playing limited). The more quadrants a card helps you in, the better.
* Developing: This is the state in which both players have almost no board presence. Typically the start of the game or just after a player played a board sweeper
* Parity: Both players have considerable board presence. Generally if one attacks the other will likely establish favorable blocks and acquire superior board presence. Creatures with evasion are important in this board state.
* Ahead/winning: You have a board presence that is kicking your opponent's ass. This is the least important board state to care about when deciding which cards should go in your deck.
* Behind/losing: Your opponent’s board presence is kicking your ass. Cards that fit in this category aren't exactly common. [http://mtgsalvation.gamepedia.com/Wrath_effect Wrath effects] can usually help you out in this situation.