Yesterday, the Federal Reserve announced the purchase of 300 billion dollars in bonds.
This is called Quantitative Easing.
Why did the FED do that?
Here is a practical and easy explanation provided by the Fincial Times. I thought it was cute.
http://www.ft.com/cms/s/0/8ada2ad4-f3b9-11dd-9c4b-0000779fd2ac.html