  Money is a conventional medium of exchange. Given an array of goods for sale at various prices, with some money one has the option to purchase any combination of these goods, within the budget constraint set by the amount of money one has. What money can purchase in a given society depends on the state of its economy and also on legal and cultural norms that may limit in various ways what is allowed to be put up for sale. For example, the laws may forbid the sale of sexual activity, human organs intended for transplant, the right to become a parent of a particular child by adoption, narcotic drugs, and so on. What money can purchase also obviously depends on what one is free to do with whatever one purchases—one may catch fish with the fishing rod one purchases only with a license and in accordance with rules issued by the state agency that regulates fishing.