“The Fed has been buying bonds since early 2009. When a private investor buys bonds, the investor uses cash or sells some existing asset to raise cash and uses that money to buy bonds. The investor might also borrow money from a bank and use the borrowed funds to buy securities on margin. The Fed can do something else. It has the power to electronically credit money to the bank accounts of sellers who in turn sell government securities or mortgage backed securities to the Fed. The banks get the money and the Fed gets the securities. The Fed isn’t literally printing $100 dollar bills when it does this. But it is creating money, electronically, that wasn’t in the financial system before. In that sense, it is printing money.” Read more.