A patron saint is a saint who is regarded as the intercessor and advocate in heaven of a nation, place, craft, activity, class, or person. Patron saints, because they have already transcended to the metaphysical, are able to intercede effectively for the needs of their special charges. Some consider it a special devotion to God by displaying humility in asking a saint for intercession instead of being answered themselves. 
"Patron Saints". Catholic Encyclopedia. New York: Robert Appleton Company. 1913. http://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/Patron_Saints.
A patron saint is someone who has their whole life to something greater than themselves. They are someone who worked hard to make the world a better place. Catholics traditionally take a name of a patron saint to help them throughout their life.
Here is a list of patron saints and the things that they are the patron saint of: