It's very simple. If you buy everything with a credit card. You don't need money. But you will incur debt. In the US, we have had several wars (one we are still having), Medicare Part D and many other programs that were never funded.
We sell treasury bonds to other countries and other big moneyed interest. That's our credit card. There are two types of investments: equity and debt. Equity is where you own something, like stocks and debt is where the holder of the bond is lending you money and you pay off the loan, usually with interest.
In general, money is never really printed to increase the money supply. They sell bonds and the Federal Reserve raises and lowers the interests rates to regulate supply and demand, which in turns tries to regulate inflation.
In the Eurozone, they have a Central bank that lends the member countries money, that basically does the same thing that we do.
I started out saying this was simple and now I'm getting all involved. I hope this helps. For others out there, if this is not a correct explanation, please feel free to correct me.