[1] In active portfolio management, the aim is to maximize the relative return (often subject to a risk constraint).
Conversely, when the relative return is negative, the portfolio is said to underperform the benchmark.
Within passive portfolio management, the absolute value of the relative return is often called the tracking error, which is confusing since the tracking error is more generally defined as the standard deviation of the relative return.
Index funds are the financial products that use passively managed portfolios.
Also, because investment returns are largely due to chance, a portfolio manager's historical performance is not a good indicator of skill.