kaas - the most important word to know when you're in the Netherlands. So that you can go the kaas shop and buy the WHOLE SHOP.
Why "Jij" instead of "Je"?
Both of them are correct. "Jij" is the stressed version of the pronoun, intended to distinguish between you and somebody else. "Je" is the unstressed version, used when it is obvious who you are talking about. See here for more info.