[kpreid]

The metagame (or "the meta") is the long-term game in which the moves are "I am going to play this character/deck and practice/use these strategies" -- decisions you make at the beginning, or before, play starts in the base game and the rounds are complete games of the base game.

Learning new information about the base game (or it being updated by the developers) changes what moves are best in the metagame — but as this knowledge propagates through the player base, the probability distribution of what-you-will-be-facing changes, which also changes the best choices of meta-moves.

For an example of why metagames are more than just knowledge about the base game, suppose that we have a fighting game with character A (or a CCG with a player-designed deck A) who is well-rounded and B who doesn't do so well in most cases but is good at beating A. Then even if the base game doesn't change at all and nobody learns a new trick, B is a good choice if and only if lots of other people are playing A — meaning you have a dynamical system.

A lively metagame keeps things interesting because players keep doing new (or dusting off old) things to defeat the current things, rather than sticking to what works — because "what works" changes. It avoids the problem of "X is best, so either you ignore other parts of the game or you are deliberately playing suboptimally".