This quote is trying to explain that fame and success are not the same things. Madonna is a famous celebrity, meaning that she is well-known and has a lot of influence in popular culture. However, she may not necessarily be seen as someone who is successful, which could mean that she has not achieved many of her goals. Helen Keller, on the other hand, did not become famous, but she was very successful in achieving her goals, having been an activist for disability rights and a major influence for the disability rights movement.