Money market fund
A mutual fund that holds short-term debt and cash. It aims to stay stable but is an investment, not an insured deposit.
Money market funds are sold by brokerages and fund companies and buy things like Treasury bills and other short-term debt. Many people use them to hold cash in a brokerage account.
Unlike a money market account at a bank, a money market fund is not FDIC insured and can lose value, even though that is rare.