The recent historical money printing (bonds have to be repaid, and not technically printing) is QE = Quantitative Easing. The Fed makes up money, and uses it to buy real bonds, under the theoretical possible future of reselling the bonds later. It gives the interest paid on those bonds back to the treasury. While the activity is absurd, it tends to inflate bond prices (lower interest rates) because easy money is to buy bonds before Fed buys them back from you.