Final answer:
The three biggest social insurance programs in the US are Social Security, Medicare, and Medicaid, which provide financial support and healthcare to the elderly, disabled, and low-income individuals.
Step-by-step explanation:
In the US, the three biggest social insurance programs are Social Security, Medicare, and Medicaid. These programs are essential components of the federal government's efforts to provide financial support and healthcare to specific groups of Americans. Social Security, officially known as Old-Age, Survivors, and Disability Insurance (OASDI), is primarily funded through a dedicated payroll tax and provides benefits to the elderly, disabled, and survivors of deceased workers. Medicare is a healthcare program that serves people over 65 and those with certain disabilities, while Medicaid offers healthcare to individuals and families with low incomes who meet specific eligibility criteria.