These are government-insured accounts that allow you access to the money you have deposited. Withdrawals are limited to six monthly, three of which may be by check. These accounts earn interest with the rate varying widely. Banks that are trying to attract deposits often offer MMAs yielding in excess of 5 percent. The average yield nationwide is often half that.
Yield also depends on the amount deposited.
Money market funds are a type of mutual fund. That value never changes. But the return on the investment does fluctuate. Earnings are paid as dividends to shareholders. Although the deposits made in these funds by shareholders are not insured by the government, money market funds are a relatively secure investment.