A certificate of deposit account is simply another deposit product available at banks, alongside savings, money market, and checking accounts. But instead of depositing money that you can withdraw from or add to whenever you want, you can generally only make a single initial deposit to a CD. When you open one, you're making an agreement to keep your funds in the account without withdrawals for an established period of time, known as the CD term. The trade-off to committing your funds is that you are able to lock in your interest rate. While a savings account rate can change whenever the bank sees fit, opening a CD involves the bank making a written promise on the interest rate it’ll pay you for the duration of the term. CDs are typically offered in standard maturity terms from 1 month to 10 years, with the most common terms ranging from 6 months to 5 years. But note that a bank can offer a CD in any term it wants. In fact, sometimes the top national rate is for an odd-term certificate—say, 5 months or 19 months—that is being offered as a limited-time promotion.