Index funds provide you with a way to invest in the stock market that is completely passive. For example, if you invest money in an index fund that is based on the S&P 500 Index, you will be invested in the general market, without having to concern yourself with choosing investments, rebalancing your portfolio, or knowing when to sell or buy individual companies. All that will be handled by the fund which will base the fund portfolio on the makeup of the underlying index.
The U.S. Internal Revenue Service categorizes income into three broad types, active income, passive income, and portfolio income. It defines passive income as only coming from two sources: rental activity or "trade or business activities in which you do not materially participate." Other financial and government institutions also recognize it as an income obtained as a result of capital growth or in relation to negative gearing. Passive income is usually taxable.
Managerial accounting defines residual income in a corporate setting as the amount of leftover operating profit after all costs of capital used to generate the revenues have been paid. It is also considered the company's net operating income or the amount of profit that exceed its required rate of return. Residual income is normally used to assess the performance of a capital investment, team, department or business unit.