What is the Fountain of Youth Anyway?

I think people talk about "looking for the Fountain of Youth" as though they certainly know what it is and what it can do. But do you really know what you're looking for?
The way I understand it, One of the sailors who sailed with Christopher Columbus on his second voyage to the New World was a man named Juan Ponce De Leon. This voyage would change his life.
He decided to stay in Hispaniola when Columbus returned. Ponce became very popular and was named governor of neary Puerto Rico then called (Boriquien) in 1508.
While there, he heard many stories of a magical water source. People called it the "Fountain of Youth" and said that drinking its water kept you young. Ponce decided that he must find this water source.
For the next few years, he tried to find out where this "Fountain of Youth" was. He finally believed he knew where it was, and he asked permission from Spain's King Charles V to go in search of it. The king agreed, as long as Ponce agreed to pay for the ships and crew. (to be cont.)