Active Income

You work. You actively haul bricks. You actively correct lens optics on telescopes in space. You actively work, so you actively earn income, on which you're actively taxed at ordinary income rates by the kindly, loving people of the IRS.

Specifically, when you're active, the IRS views you as taxable fodder if you work 500+ hours in the year. The key concept maps to passive income, which is just income derived from investments, i.e., things like dividend income, bond interest, and rent payments. Those would be passive income elements, even if you had to work really hard to collect the money.