Bonds.
Companies finance their activities by way of internally generated cash flows. If they need to raise more money they can borrow money, usually by issuing bonds. Companies generally use an investment bank to issue their bonds and to find buyers.
Bondholders get back their original investment on a fixed maturity date and receive their interest payments. Bonds are generally safer than stocks or shares, but in the medium or long time, shares pay a higher return than bonds. For companies, the advantage of debt financing over equity is that bond interest is tax deductible.