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. In addition to its role in social security, the SSN is often required for various purposes, such as opening bank accounts, applying for loans, and filing taxes. It helps government agencies and businesses verify a person's identity and track their financial history.