The U.S. federal government releases its own bonds from the treasury and from numerous federal government firms. Those developing in less than one year are called T-bills. Bonds that mature in one to 10 years are T-notes, and those that take more than 10 years to mature are treasury bonds. In many cases, you don't need to pay state or regional earnings taxes on the interest they earn.
Munis finance things like health centers, schools, power plants, streets, workplace buildings, airports, bridges and so on. Municipalities typically issue bonds when they need more money than they gather through taxes. The excellent thing about community bonds is that you do not need to pay federal earnings taxes on the interest they make.