Lending Club is a platform where you can lend your money to other people. You’re the bank. Each note is only $25, so you can invest $1,000 and lend money to 40 people. There are many grades of loan (from safest to riskiest) and investors earn, on average, between 5% and 7% annualized returns. For more information, check out Investing and Making Money with Lending Club Peer-to-Peer Lending and my real money Lending Club Portfolio.
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.