In a fiat money system, money is not backed by a physical commodity (i.e.: gold). Instead, the only thing that gives the money value is its relative scarcity and the faith placed in it by the people that use it. A good primer on the history of fiat money in the US can be found in a video provided by the Mises.org website.
In a fiat monetary system, there is no restrain on the amount of money that can be created. This allows unlimited credit creation. Initially, a rapid growth in the availability of credit is often mistaken for economic growth, as spending and business profits grow and frequently there is a rapid growth in equity prices. In the long run, however, the economy tends to suffer much more by the following contraction than it gained from the expansion in credit. This expansion in credit can be seen in the Debt/GDP ratio.
http://kwaves.com/fiat.htm
"One man gives freely, yet gains even more; another withholds unduly, but comes to poverty. A generous man will prosper; he who refreshes others will himself be refreshed." Rev Canon Karanja.