A bond is a debt obligation. Investors who buy corporate bonds are lending money to the company issuing the bond. In return, the company makes a legal commitment to pay interest on the principal and, in most cases, to return the principal when the bond comes due, or matures.

To understand bonds, it is helpful to compare them with stocks. When you buy a share of common stock, you own equity in the company and will receive any dividends declared and paid by the company. When you buy a corporate bond, you do not own equity in the company. You will receive only the interest and principal on the bond, no matter how profitable the company becomes or how high its stock price climbs. But if the company runs into financial difficulties, it still has a legal obligation to make timely payments of interest and principal. The company has no similar obligation to pay dividends to shareholders. In a bankruptcy, bond investors have priority over shareholders in claims on the company's assets.

Like all investments, bonds carry risks. One key risk to a bondholder is that the company may fail to make timely payments of interest or principal. If that happens, the company will default on its bonds. This "default risk" makes the creditworthiness of the company—that is, its ability to pay its debt obligations on time—an important concern to bondholders.

A high-yield corporate bond is a type of corporate bond that offers a higher rate of interest because of its higher risk of default. When companies with a greater estimated default risk issue bonds, they may be unable to obtain an investment-grade bond credit rating. As a result, they typically issue bonds with higher interest rates in order to entice investors and compensate them for this higher risk.

High-yield bond issuers may be companies characterized as highly leveraged or those experiencing financial difficulties. Smaller or emerging companies may also have to issue high-yield bonds to offset unproven operating histories or because their financial plans may be considered speculative or risky.

Municipal bonds (or “munis” for short) are debt securities issued by states, cities, counties and other governmental entities to fund day-to-day obligations and to finance capital projects such as building schools, highways or sewer systems. By purchasing municipal bonds, you are in effect lending money to the bond issuer in exchange for a promise of regular interest payments, usually semi-annually, and the return of the original investment, or “principal.” A municipal bond’s maturity date (the date when the issuer of the bond repays the principal) may be years in the future. Short-term bonds mature in one to three years, while long-term bonds won’t mature for more than a decade.

Generally, the interest on municipal bonds is exempt from federal income tax. The interest may also be exempt from state and local taxes if you reside in the state where the bond is issued. Bond investors typically seek a steady stream of income payments and, compared to stock investors, may be more risk-averse and more focused on preserving, rather than increasing, wealth. Given the tax benefits, the interest rate for municipal bonds is usually lower than on taxable fixed-income securities such as corporate bonds.

The two most common types of municipal bonds are the following:

• General obligation bonds are issued by states, cities or counties and not secured by any assets. Instead, general obligation are backed by the “full faith and credit” of the issuer, which has the power to tax residents to pay bondholders.
• Revenue bonds are not backed by government’s taxing power but by revenues from a specific project or source, such as highway tolls or lease fees. Some revenue bonds are “non-recourse”, meaning that if the revenue stream dries up, the bondholders do not have a claim on the underlying revenue source.

In addition, municipal borrowers sometimes issue bonds on behalf of private entities such as non-profit colleges or hospitals. These “conduit” borrowers typically agree to repay the issuer, who pays the interest and principal on the bonds. In cases where the conduit borrower fails to make a payment, the issuer usually is not required to pay the bondholders.