Passive income differs from earned income and portfolio income in a variety of ways. Passive income is generally defined as a stream of income earned with little effort, and it is referred to as progressive passive income when there is little effort needed from the individual receiving the passive income in order to grow the stream of income. Examples of passive income include rental income and any business activities in which the earner does not materially participate during the year.
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.