Question 1: What is the difference between this (government issues
bonds and the central bank buys them) and directly printing money?
Answer 1: Same as EnergyNumbers pointed, the difference is that in
buying the bond, the central bank now owns a bond, but when the
central bank printed the money, they just printed and inject the money
to the economy.
One of the purpose of the central bank is, they control the amount of printed money in the economy, to create a stable economy.
If there are too much printed money in the economy, then, the value of the printed money is fall. They call it "Inflation", and hyperinflation if the inflation is too much. When inflation happen, the price of goods and services is rise high. When the goods and services are rise high, the goods and services are too expensive. There will be many protester in the street.
If there are too little printed money in the economy, then, the value of the printed money is raise. So the same money can buy more goods and services, but the companies don't like it, because the goods they have produced now are low in value, so they decrease the production of goods. When they decrease the production of goods, the want to lay off the workers, when they lay off many workers, the situation is bad, many demonstration in the street. They call this phenomena as "Recession".
When they are too much printed money in the economy, the economy is unstable. So to make it stable again, we must decrease the printed money in the economy. How? Well, one of the three methods used is:
- The central bank sell a new bonds to the citizen, and when the citizens or companies or banks buy the bonds, they give the money to
the central bank. Now, the central bank can keep the printed money in
their vault, thus, decreasing the printed money in the economy.
When they are too little printed money in the economy, the economy is unstable. So to make it stable again, we must increase the printed money in the economy. How? Well, one of the three methods used is:
- The central bank buy back the bonds from the citizens, companies, banks. The central bank give the money to them, thus, increasing the printed
money in the economy (in effect creating money).
Source: http://www.investopedia.com/ask/answers/07/central-banks.asp , https://www.youtube.com/watch?v=y1OJlJ9COg0