Who does the "Jack" rep. in cards?

Factual Questions
1

I understand what a King and Queen are, but what is a Jack? Is he the son? No, that would be a Prince. I would have made this card a Knight, personally. So, in this case, what is the Jack? A nobleman, perhaps? - Jinx

2

Answered here

http://www.cs.man.ac.uk/playing-cards/jack+knave.html

3

That’s a very interesting site BTW. Well worth a bookmark