United States bonds are bonds that are issued by the government of the United States of America.  When a purchaser buys US bonds he is purchasing the debt of the US government and is in fact loaning money to the US.  These types of investments are considered the safest of all investments.  There is over $3 trillion in US bonds, bills, and notes on the market.  US bonds are very safe and predictable and the most liquid of the debt market.  One advantage US bonds has over other bonds is that they generally do not include call provisions.