Here is the heart of the matter from Wiki:
In practical terms, the central bank purchases financial assets, including treasuries and corporate bonds, from financial institutions (such as banks) using money it has created ex nihilo (out of nothing).You have to watch that "out of nothing" part. Conservation of matter and energy and all that stuff.
The government just waves it's magic wand and "poof" a rabbit or a trillion dollars just appears out of thin air. The difference is that the magician is putting on a show to entertain you while the government's actions are not entertaining. In the end it will be your checkbook that is put in the box and cut in half.
Are you ready?