The name of the game

자료: Cambridge International Dictionary of Idioms © Cambridge University Press 1998, http://idioms.thefreedictionary.com/name+of+the+game

the most important part of an activity, or the quality that you most need for that activity. You have to know the right people in acting. That's the name of the game.

자료: http://www.answers.com/topic/the-name-of-the-game

he crux of the matter; also, the main goal. For example, 

• Getting them to admit they're wrong--that's the name of the game, or 
• Parents don't approve of a coach who insists that winning any way one can is the name of the game. 

This rhyming idiom uses name in the sense of "identity." [Mid-1900s]