Certificate of deposit (CD): An insured, interest-bearing deposit at a bank, requiring the depositor to keep the money invested for a specific length of time.

A Certificate of Deposit CD generally pays a higher interest rate than a regular savings account in exchange for a commitment to keep the money deposited for a specific period of time.

A certificate of deposit or CD is a time deposit, a financial product commonly offered to consumers by banks, thrift institutions, and credit unions.

CDs are similar to savings accounts in that they are insured and thus virtually risk-free; they are “money in the bank” (CDs are insured by the FDIC for banks or by the NCUA for credit unions). They are different from savings accounts in that the CD has a specific, fixed term (often three months, six months, or one to five years), and, usually, a fixed interest rate. It is intended that the CD be held until maturity, at which time the money may be withdrawn together with the accrued interest.

http://en.wikipedia.org/wiki/Certificate_of_deposit