A Social Security number (SSN) is a unique identifier assigned to individuals in the United States. It is primarily used for tracking earnings and benefits within the Social Security system, which provides financial support to retirees, disabled individuals, and survivors of deceased workers. The SSN is also essential for various purposes, such as opening bank accounts, applying for loans, and filing taxes. It helps government agencies and financial institutions verify a person's identity and manage their records. Protecting your SSN is crucial, as it can be misused for identity theft if it falls into the wrong hands.