A more thorough explanation:

The Bank Secrecy Act is a federal law that requires banks and other financial institutions to keep records of their customers' transactions and report certain domestic and foreign transactions to the government. The law was passed by Congress in 1970 to assist the federal government in criminal, tax, and other regulatory investigations.

For example, if a customer deposits a large sum of money into their bank account, the bank is required to report this transaction to the government. Similarly, if a customer transfers a large amount of money to a foreign bank account, the bank must also report this transaction.

These examples illustrate how the Bank Secrecy Act helps the government track financial transactions and prevent illegal activities such as money laundering and terrorist financing.