1. The verb нравитьса-понравиться means 'to like', 'to be impressed' by something or somebody.
  2. The person who receives the impression will be in the dative case, while the person liked will be the subject of the sentence and therefore in the nominative case:
    Сергею понравилась ваша тётя.
    Sergei was impressed by you aunt.
    Kак вам нравится наш дом?
    How do you like our house?