Many people like writing blogs but only a few know that it can fetch you money as well. You can sign up with different companies as a promoter (or an affiliate) to promote their certain product or services on your blogs and websites. The payment method can be either a flat fee or a percentage of the amount of the sale completed, depending on your agreement.
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.