Social Security is a key component of people's retirement income. But millions of Americans who rely on the program don't know everything they should about Social Security.

In the following video, Dan Caplinger, the Fool's director of investment planning, runs through three essential aspects of Social Security. Dan begins by describing the fact that Social Security's benefits are progressive, giving those with low average earnings a bigger percentage of their pre-retirement income than higher-income earners. In addition, he discusses how some people aren't eligible for Social Security. Finally, Dan looks at the Social Security Trust Fund, noting that unlike investors in the iShares Barclays 20+ Year Treasury ETF (NASDAQ:TLT) or iShares Barclays TIPS Bond ETF (NYSEMKT:TIP), Social Security doesn't lose money on the bonds it holds when rates rise and could actually benefit from higher rates in the long run.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.