Debt is what someone owes to someone else. Usually, debt is in the form of money, but it can also be items, services, favors, or other things. Thus if you make an agreement to give or do something for someone else, you now owe a debt. Unpaid debt can lead to problems such as the Greek government-debt crisis. Debt is used by many corporations and individuals to make large purchases that they could not afford under normal circumstances. Popular types of debt owed by households and individuals are mortgage loans, car loans, credit card debt, and income taxes. In the case of individuals, debt is a way to use an anticipated income combined with the future purchasing power at present before earning the same.