Buy Bonds and Make Money
A bond is a debt obligation and is considered borrowing money. You need to repay the money in the bond (also called a loan) to the issuer of the loan. And just like a loan, you pay interest. Most bonds are purchased by lenders. A lender could be you. The issuer could be the federal government.
The reason to buy a bond is to lend money to be able to fund your venture/business. You may have your government sell a bond and use the money to fund government ventures such as building businesses, funding a conference or building street lights. A business may sell you a bond as well to create an investor in their business. The sold bonds represent an interest in the business creating an investor. With so many investors they then have enough capital invested in the business that they can do what they had proposed to do.