Credit default swaps (CDS) are the most common type of credit derivative. Thispaper provides a brief history of the CDS market and discusses its main characteristics.After describing the basic mechanics of a CDS, I present a simple valuation framework thatfocuses on the relationship between conditions in the cash and CDS markets as well as anapproach to mark to market existing CDS positions. The discussion highlights how the 2008global financial crisis helped shape currentpractices and conventions in the CDS market,including the widespread adoption of standardized coupons and upfront premiums and theincreased reliance on centralized counterparties. I also address CDS indexes--focusing ontheir growing role as key indicators of investors’ attitudes toward credit risk--and brieflyexamine their behavior during periods of acute financial or economic dislocations, includingthose associated with the COVID-19 pandemic.