Certificates of deposit are a special type of savings account that have boosted interest rates in exchange for keeping your funds locked up for a fixed amount of time. The reason banks and credit unions are willing to pay higher rates on CDs is because they can generally count on those funds staying in the account, unlike funds that can unpredictably come and go in a savings, money market, or checking account. Banks and credit unions offer CDs in a variety of terms, from 1 month up to 10 years, so you can choose how long you're willing to lock up your funds. The most common CD terms, however, range from 6 months to 5 years, with 1-year certificates being the most widely available of all. The date your CD ends is called its maturity date, and although it’s not impossible to withdraw your funds before maturity, you’ll incur a financial penalty if you do so.