That is, you lend money to others (companies) and they give you fixed interest. No matter how much money they make from their investment, how much money they lose has nothing to do with how much money they pay you back. If the company goes bankrupt, they will return the money to the borrower (bondholder) at the time of settlement. Of course, there are several types of debt investment. Generally, the creditor with the lowest interest rate is the first person to be repaid when the company goes bankrupt. Some creditor investors can't get any money even if they go bankrupt (in this case, there is no money for the creditor with priority), but the interest of such creditor investors is higher because they bear higher risks.