Final answer:
A fiduciary is an institution or person responsible for making all investment, management, and distribution decisions in an account maintained in the best interests of another.
Step-by-step explanation:
An institution or a person responsible for making all investment, management, and distribution decisions in an account maintained in the best interests of another is known as a fiduciary. A fiduciary has a legal and ethical obligation to act in the best interests of the account holder and must prioritize their interests over their own.