@The Cook It's not required to have played the game, just wiki it and it will tell you more of the game. :)
But the basic plot of the game is you play as a guy named Joel twenty years ago was when an new outbreak of cordyceps happens (A real disease by the way but doesnt infect humans only small bugs) happened, he and his daughter at the time were trying to escape the city that they were living in, he ends up losing his daughter. Twenty years later in a safe zone in he is given a job to smuggle a girl named Ellie out of the city, but he quickly finds that she is infected herself but is immune to the infection, and he escorts her across the US to where they could possibly make a cure.