How is social security an example of income redistribution?

Social Security is a government redistribution program. It works something like this:

All people between the ages of 18 (threshold of adulthood) and 62 (age of "retiree") pay a tax based on their income to the Social Security fund

All people over the age of 62 collect a monthly check from the Social Security fund depending on their situation (married, number of dependents etc).

This essentially means the money is being redistributed from youthful wage-earners to elderly retirees.