I like ximenez's writeup above but his (her?) answer, imho, refers to the creation of wealth, not the creation of money.

Wealth is indeed created by increases in productivity and efficiency and of better use of natural resources. Money, however, is created by central banks and by banks in general.

To sum the current fiat money situation we have now in a sentence - "Money is created by issuing debt".
If you understand this, you understand the nature of money.

shokwave: uhuh. currency is another thing altogether. It's the stuff that the government prints (on plastic or paper) that usually has the words "this bill is legal tender for ..."