The primary fairies in the play are Oberon and Titania, king and queen of the fairies, respectively. The fairies are immortal, unlike the humans in the play. The fairies' lives become intermingled with the mortals' lives in this play.
The fairies are very human in many regards. They look very much like humans, first of all. Secondly, they have human emotions and feelings. The experience love, jealousy, desire, anger, etc. This is apparent with Oberon's and Titania's jealousies of each others affairs with Hippolyta and Theseus. Oberon is also jealous of Titania's relationship with her new child she was given when one of her handmaids died. Oberon wanted the child for himself, so he exacts revenge on her via a magic flower "juice".
As you can see the fairies are so similar to their human counterparts. The main difference is that the fairies are immortals.