Collateralized debt obligations (CDOs) are financial instruments that are created by pooling together various debt instruments and then repackaging them into different tranches that are then sold to investors. CDOs are typically backed by assets such as mortgages, corporate debt, and other financial instruments.

Collateralized debt obligations (CDOs) are a type of structured financial product that pools together various types of debt, such as mortgages, corporate bonds, and other debt instruments, and then repackages them into a single security. CDOs are typically divided into tranches, or slices, with each tranche having a different level of risk and return. The most senior tranche is the safest and has the lowest return, while the most junior tranche is the riskiest and has the highest return.
CDOs are created by investment banks, which purchase the underlying debt and then package it into a single security. The investment bank then sells the CDO to investors, who can purchase the entire CDO or individual tranches. The investment bank also typically provides a credit enhancement, such as a letter of credit, to ensure that the CDO is able to meet its obligations.
CDOs are attractive to investors because they offer a higher return than traditional debt instruments, such as bonds. They also provide diversification, as the underlying debt is spread across a variety of different debt instruments. However, CDOs are also riskier than traditional debt instruments, as they are subject to the risk of default on the underlying debt.
CDOs were popular during the mid-2000s, but their popularity declined after the financial crisis of 2008. This was due to the fact that many CDOs were backed by subprime mortgages, which defaulted at a higher rate than expected. As a result, many investors lost money on their CDO investments.
Despite the risks associated with CDOs, they remain an important part of the financial system. They provide investors with an opportunity to diversify their portfolios and earn higher returns than traditional debt instruments. However, investors should be aware of the risks associated with CDOs and should only invest in them if they are comfortable with the potential losses.