1. -어요

    1. '-어요' is a polite, informal ending.
    2. '-어요' follows syllables containing the vowels '어','여','우', '유','으','이' ('Yin' or dark vowels)
      있|어요 ? Do you have (it) ?
      있|어요. I have (it).
      없|어요 ? Don't you have (it) ?
      없|어요. I don't have (it).

  2. -이요 ?

    1. '-이요?' is a polite ending meaning "You are talking about - ?"
    2. '-이요' is used when asking for or giving confirmation or repeatition.
    3. '-이요' follows nouns which end with a consonant.
      그 사람|이요? You are talking about him?
      그 사람|이요. I am talking about him.
      이 책|이요? You mean this book?
      이 책|이요. I mean that book.

  3. -은

    1. '-은' is used for emphasizing a subject or an object.
      It also marks the general topic of the sentence.

    2. '-은' follows syllables that end with a consonant.
      없어요. There isn't.
      신문 없어요. I don't have a newspaper.
      신문은 없어요. I don't have a newspaper
      (but I might have something else).
      여기 신문은 없어요. There aren't any newspapers here
      (but there might be some other things).