ELI5: Explain Like I'm 5

Central securities depository

A central securities depository (or CSD) is like a bank for stocks and bonds. It is a company that holds (stores) the ownership records for stocks and bonds. The CSD also helps to move stocks and bonds between different people, like when you buy stocks or bonds from someone else. All the records and transfers are done safely and securely so that people don't lose any money or have any problems with their investments.