The era of quantitative easing is over, for now, and in the United States, at least. But the consequences of the Federal Reserve’s policy to pump trillions of dollars into the financial system in hopes of stimulating the economy will long be with us.

Fed policy makers met Wednesday and announced that October would conclude their third round of using dollars created out of thin air to buy vast sums of bonds — $1.7 trillion in just the third round of the program, known across the land (or at least the financial world) as QE3.

The program has managed a rare trick of being perpetually maligned on Wall Street while driving asset prices up enough to make lots of people on Wall Street very wealthy. But what do we know about these three programs that eased monetary policy through unconventional means?

The Fed faces a paradox. Its goals are all related to the real economy. It is charged by law with maintaining stable prices and maximum employment. But its tools work through financial markets, principally buying and selling bonds.