You play from both the sides. You play as Ellie and then you play as her enemy, Abby. The emotions in the game will grab you so hard that it will be hard for you to decide which side to choose. I never played a game before where i had trouble choosing which side to support.
This game is not for people who want action right from the start. This is not Call of Duty. This game is story driven. The game is long and will make you chew your nails sometimes.