Minority game can be regarded as an Ising Model for system of heterogeneous adaptive agents, who interact through a global mechanism which involves competition for limited resources as in financial markets, for this reason it can be qualifies as a complex systems. Markets are institutions which allow agents to exchange goods. Through these exchanges, traders can reallocate their resources in order to increase their profit. Since trading itself does not create wealth, the market must be a zero sum game. Taking out transaction costs and other frictions which are needed to reward the market maker for the service he is providing, the game becomes a Minority Game.