There are many different bond types and in multiple formats, because in general they tend to bond is issued in accordance with funding requirements and the ability to pay future debts of the issuer. At the same time, they should have to respond to the different needs of each investor, retirement age, people who do not want to risk may want to invest in a government bond that is not long. For high stability, even if they are to yield relatively low. While people start working age risk more than they can be invested in the private sector debt, high yield, but there may be more at risk, etc.