A Social Security Number (SSN) is a unique nine-digit number assigned to individuals in the United States by the Social Security Administration. It is primarily used to track 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 serves as a key identifier for individuals in many aspects of life, making it essential for accessing services and benefits in the U.S.