The Social Security Act was a law passed in 1935 that set up the Social Security system that continues to exist in the US to this day. The system has been modified at times since 1935, but the basic set up remains the same.
The Social Security Act set up a system whereby workers would pay into a fund while they were working. After they reached a certain age, they would be eligible to draw from that fund. These payments would be available to all, regardless of income or wealth. Payments would continue for the life of the retiree. A person who lived a long time after retiring would continue to receive payments, even if they exceeded what he or she had paid into the system.
The point of this Act was to ensure that future generations of older Americans would not be likely to face poverty after they retired.
The Social Security Act of 1935 was part of the New Deal program of reforms. It created a federal pension system funded by taxes on worker's wages and by an equivalent contribution by employers.