Interdependence occurs when people depend on one another. Specialization brings about interdependence. The United States makes cars and sends cars to China. Taxes are the money the government collects from individuals and businesses to pay for public goods and services. This man dislikes paying his taxes.
Money is a medium of exchange which makes trade easier.
It is a store of value which allows people to save the income from their efforts given up. Opportunity cost is the real choice. When deciding how to spend a resource it is one's second best alternative, the alternative given up or the lost opportunity. The amount of money one must give to buy a good or service. What a seller receives for a good or service.