Series EE savings bonds were introduced in 1980 to replace the series E bond. They are sold at a discount to their face value. The interest on series EE bonds purchased since 1989 is exempt from federal and state taxes if it is used for education expenses. Since December 11, 2001, series EE bonds have been inscribed with the words "Patriot Bonds."
Series I Bonds are sold at face value and grow in value with inflation-indexed earnings for up to 30 years. I Bonds gain interest once a month, with interest being compounded twice per year. The composite interest rate has two components (multiplied, not added): a guaranteed fixed rate, which does not change over the 30 year period; and a semiannual inflation rate, which is adjusted twice per year. Even in times of deflation, the composite interest rate is guaranteed never to go below zero, meaning an I Bond's redemption value can never go down.
from
http://en.wikipedia.org/wiki/Treasur...#Treasury_bond
I know nothing personally about bonds.