Usually referring to a personal life story, rags to riches is generally a tale of abject poverty that teaches that through hard-work and dedication one will eventually receive wealth and prosperity. Such stories are a cornerstone to and supposed proof of the American Dream. Of course the Philosophy also applies to many other people and groups of people throughout history.
This philosophy is still taught to children today. It is the supposed reason why a person should work hard at school, work etc.
A few noteworthy figures whose lives reflect a rags to riches life are, Obama, Oprah, and Frank McCourt. I am quite sure that there are more but I can't think of any.