What medical insurance knowledge do the elderly who immigrate to the United States have?

Immigrants from Australia and Australia: It is unthinkable to support the elderly in the United States without medical insurance. However, if there is public medical insurance, everything will be much easier. The welfare policy for the elderly in the United States stipulates that the elderly over 65 basically do not have to pay much medical expenses, and the cost of hospitalization is also very small. However, the premise of all this is to join the two major public medical insurance systems-Medicaid and medical insurance.