"For the first time ever we’ll be offering single player DLC. The journey and cast of characters in The Last of Us lends itself to thorough narrative exploration and we’ve got more of the story to tell."
The season pass is 20$ on PlayStation store. You can access it in game and will take you to the store to purchase. As far as I know they will only have 3 dlc for the game at least that's all ND has said so far. The season pass will let you download those dlc as they are released. If they add more dlc then they will probably do a second season pass. The season pass is not included with the game except maybe for one of the special editions but that I do not know. There is no dlc released as of yet. The 3 being released will be 1 sp and 2 mp dlc's