Money market instruments include:
Treasury Bills (T-Bills): It is issued by the government. Though they involve zero risk, the returns offered by them are relatively small in amount.
Certificate of Deposit (CDs): This is a form of time deposit that a bank grants. Their rate of interest is higher than a savings account.
Commercial Paper (CP): Commercial paper is an obligation note that an enterprise gives to raise some excess return with excess risk involved.
They are good for emergencies or as a cash management tool. However, they are not good for long-term investment because the return is minimal.