Junk bonds are fixed-income instruments that carry a rating of 'BB' or lower by Standard & Poor's, or 'Ba' or below by Moody's.
Junk bonds are so called because of their higher default risk in relation to investment-grade bonds. But as you can expect, Junk bonds could produce impressive returns.
The biggest Junk Bond ETF is iShares IBOXX $ High Yield Corporate Bond (HYG), its yield is close to 6%.
Next up, closed end funds.