May I see the answers you can choose from? This is likely to be a multiple choice question, and I can't help without knowing the full question.
What:?
When: 1871
What:?
Why?
1) Vietnam war was officially ended whereas Korean War ended in a Cease-Fire which means it never ended in official way
2) Korea was a short war and Vietnam was a Long war
3) Korea was like WW2 Whereas Vietnam was similar to Guerilla War
Hope this helps!