Investment Grade Debt
Bonds rated in top 4 categories BBB or Baa or higher. The only quality purchased by institutions (banks, insurance companies) and by fiduciaries. Habe great liquidity than lower grade instruments.
High Yield Bonds
Called junk bonds, lower ratings BB or Ba or less. Additional risk of default. Volitility higher than investment grade. Higher return potential, speculative fixed income investments.
Non rated bonds
Too small to justify paying for a bond rating. Investor has to reasearch on their own.