Net Investment Income

What Does Net Investment Income Mean?
Income received from investment assets (before taxes) such as bonds, stocks, mutual funds, loans and other investments (less related expenses). The individual tax rate on net investment income depends on whether it is interest income, dividend income or capital gains.

Investopedia explains Net Investment Income
For investment companies, this is the amount of income left after operating expenses are subtracted from total investment income, and it is typically expressed on a per share basis. To find the net investment income per share of a company, divide the net investment income by the shares outstanding. This amount is the amount available to shareholders in the form of dividends.