CDs (certificates of deposit) are issued to investors by banks. The investor lends the institution money for a predetermined amount of time, and in return, they get a set rate of interest. Money market accounts — also called money market deposit accounts or MMDAs — are more similar to checking accounts, in that money can be added, the interest rate is variable, and withdrawals can be made (with restrictions) at any time.
edit How they work
edit How CDs work
With a certificate of deposit (CD), investors choose a fixed amount (called denomination of the CD) to invest for a fixed duration (the term). There is generally a $500 minimum. At the end of the investment period, the CD matures and the investors get their principal and interest back. Investors are not allowed to add any money to an existing CD; they must invest in a new CD if they want to invest more money.
edit How money market accounts work
A money market account is similar to a checking or savings account in that it is an "active" account where money can be invested — more money can be added and money may even be withdrawn. Money market accounts are therefore more liquid compared with CDs. The downside to this is that money market accounts generally offer lower interest rates. Money market accounts also have higher minimum balance requirements than traditional savings accounts.
edit Interest Rates
While money market account rates change as rates fluctuate, CDs offer a fixed interest rate for the term. CDs with higher denominations generally pay a higher interest rate. Similarly, CDs with longer maturity periods tend to offer higher interest rates. Smaller institutions and credit unions sometimes offer better interest rates, as do online-only financial institutions.
As of May 2013, the average 1-year return from a money market account is 0.04%, while the average return on a CD is 0.44% according to BankRate.com.
edit Withdrawal Restrictions and Liquidity
Funds deposited in a CD can only be withdrawn after maturity. This can range from a few weeks to several years, depending on the type of CD.
Funds deposited in a money market account can be withdrawn almost at will, but there are usually some limits to the number of withdrawals made in one month.
edit Contribution Limits
CDs do not allow individuals to add more money over time.
Additional funds can be added to money market accounts, as with a checking of savings accounts.
edit Other Services
Some banks offer checks and ATM cards with money market accounts. No such services are available with a CD.
edit Money market accounts vs savings accounts
Money market accounts are rather similar to savings accounts — both are active accounts that allow money to stay liquid. In general, a money market account tends to pay a higher interest rate in exchange for a higher minimum balance and fewer withdrawals allowed every month compared with a savings account.
edit Money market accounts vs Money market funds
Money market accounts (or deposit accounts) should not be confused with money market funds (or money market mutual funds - MMMFs). Money market funds are mutual fund investments and are not FDIC insured. Like any mutual fund, the fund manager charges a fee for administrative, sales and other expenses associated with managing the fund. This fee lowers the return offered by the fund. There is no guaranteed return in a money market fund while a money market deposit account offers a specific interest rate. The rate may vary with the market but it is always known.