Earlier, mutual fund returns were benchmarked only against the respective index's price performance. However, this wasn't ideal. Apart from capital appreciation due to stock price movements, companies also distribute part of their profits to investors through dividends. While mutual fund NAVs reflected that, the index returns (price performance) did not. Therefore, we need the total return index (TRI), which factors in both the capital gains as well as dividend payouts. SEBI has made it mandatory for mutual funds to disclose the TRI of the benchmark so that you get a better picture of your scheme's performance against its index.