Treasury bills are short-term debt securities issued by the U.S. Department of the Treasury. They have maturities ranging from a few days to one year. T-Bills are considered one of the safest investments because they are backed by the full faith and credit of the U.S. government. They are typically sold at a discount to their face value and do not pay periodic interest. Instead, investors earn a return by purchasing the T-Bill at a discount and receiving the full face value at maturity.