These have changeable interest rates. Some variable-rate CDs feature a "multi-step" or "bonus rate" structure in which interest rates increase or decrease over time according to a pre-set schedule. Other variable-rate CDs pay interest rates that track the performance of a specified market index, such as the S&P 500 Index.

Don't assume that a "federally insured one-year non-callable" CD matures in one year. It doesn't. These words mean the bank cannot redeem the CD during the first year. A "one-year non-callable" CD may still have a maturity date that is years in the future.

These give the issuing bank the right to terminate – or "call" – the CD after a set period of time, but they do not give the CD holder the same right. If interest rates fall, the issuing bank might call the CD.

If a CD is redeemed before it matures, you may have to pay a penalty or forgo a portion of the interest.