Complementary currency

A complementary currency, or alternative currency, is a medium of exchange that is accepted in much the same way as a regular currency, within a group of people or a geographical area. It is made to complement a national currency. Usually complementary currencies are not legal tender, they cannot be used in exactly the same way as money. Their use is based on all the people of the group agreeing to accept them. According to Jérôme Blanc of Laboratoire d'Économie de la Firme et des Institutions, complementary currencies aim to protect, stimulate or orientate the economy. They may also be used to advance particular social, environmental, or political goals.
There are different kinds of these currencies:
One system, called mutual credit has the idea that there's a form of credit, that is given, but that does not need banks. Another system is that of barter.
A Local exchange trading system, or LETS trades points, where one point is usually equivalent to one hour of work. This is an example for a time-based currency.
Purposes.
Alternative currencies have been made to address specific issues:
The 2006 Annual Report of the Worldwide Database of Complementary Currency Systems presented a survey of 150 complementary currency systems in which 94 respondents said that "all reasons" were selected, among cooperation, micro/small/medium enterprise development, activating the local market, reducing the need for national currency, and community development.