Resolved questions
What is YES and NO in korean?

The most common for "Yes" and "No" is 네 and 아니요.

But you also have to remember there are different words depending on the politeness level.

- - - YES - - -
예 - More polite than 네 (Formal polite)
네 - Used towards those older than you
응 - Used towards people younger than you, siblings, and close friends
어 - Quite like "Yeah" or "Uh huh" and often heard when listening to someone on the phone

- - - NO - - -
아니오 - The old way of saying "no". Commonly used in historical context.
아니요 - The modern way of saying "no"
아니 - Used towards people younger than you, siblings, & friends.

Also, take into consideration of when to say "Yes" or "No" when answering a question.

Example:
A: You don't like them?
B: No, I don't.

The above answer is in the English way of speech. But in Korean, 네 means you AGREE with the question and 아니요 means you DISAGREE with the question asked. So in Korean, you have to say "네, 싫어해요." (Yes, I don't like them.). Because you agree that you don't like them, you have to say "yes."

I hope I didn't get you confused ^^