Registered money managers are paid professionals who are responsible for handling the securities portfolios they oversee in the best interest of the institutions or individuals for whom they work. That obligation is known as fiduciary responsibility.
The specific decisions an individual money manager makes vary, depending on the portfolio in question. For example, pension funds, mutual funds, and insurance companies have money managers, as do endowments, managed accounts, and hedge funds.
The portfolio that the manager constructs and the amount and timing of the trading he or she authorizes are directly linked to the portfolio's investment objective and risk profile.