In the context of Spanish personal/individual income tax (IRPF--Impuesto sobre la renta de personas físicas), "rendimientos de capital mobiliario" is generally translated as "investment income" (includes dividends paid on shares, interest on other investments, etc.).

You can translate the other concepts as follows:

Rendimientos de trabajo--earned income; salary income
Rendimientos de capital inmobiliario--rental income
Rendimientos de actividades económicas--business income

Hope this helps.

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Note added at 1 hr (2018-05-16 11:42:17 GMT)
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Hi, to answer your question, it is my understanding that capital gains are reported under a different section of the Spanish income tax return called "ganancias y pérdidas patrimoniales" (capital gains and losses).