This contrasts with the total return, which does take into account the income generated in the portfolio.
Examples are the S&P 500 and the MSCI EAFE, which are typically quoted in terms of price return.
[1] This is clearly misleading, since, economically speaking, it is the total return that is the only thing that matters.
Whether that return is generated in the form of cash income or in capital appreciation is irrelevant as long as one can always liquidate the investment to realise the capital appreciation into cash.
For example, mutual fund investors chase the price return, and forgo valuable investment opportunities.