M-C-M means money-commodity-money. And capitalists strive off of this because they use the money they have from investments and inheritance, and buy ‘commodities’. These commodities are considered labor, and materials which helps create a product. And then these capitalists make a surplus value off of these commodities because they price the product at a higher value. And pay the laborers less money than deserved. This increases the wealth of capitalists because this process happens continuously.