U.S. TREASURY BILLS are obligations issued by the Department of the Treasury maturing in 13, 26 or 52 weeks.

U.S. TREASURY NOTES are U.S. government paper, not legally restricted as to interest rates, with maturity from one to five years.

U.S. TREASURY BONDS are long-term (10 to 30 years) fixed interest government debt security.

GOVERNMENT NATIONAL MORTGAGE ASSOCIATION (Ginnie Mae) is the name of the agency which issues and guarantees GNMA securities which are mortgage-backed certificates.  Monthly payments of principal and interest from homeowners are passed through to the investors who owns GNMA's.