A Social Security Number (SSN) is a unique identifier assigned to individuals in the United States by the Social Security Administration. 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. SSNs are also commonly used for various purposes, such as opening bank accounts, applying for loans, and filing taxes. Because of their importance, it is crucial to protect your SSN to prevent identity theft and fraud.