Offer your thoughts or opinion on the input financial query or topic using your financial background.

What is a “fiat” currency? Are there other types of currency?
There's two types of categories at play that define currency types - but I think the first is more like what you are after.  The first is there are essentially three currency types now recognised - see them described here: http://finance.mapsofworld.com/money/types/ The second is currencies can be categorised by the type of economy from which they are generated (reserve/commodity/etc) - see them described here: http://www.forextraders.com/learn-forex-trading-course/major-currency-pairs.html