The game is free the thing your looking at in the store is a pack you can buy it’s for the season pass and other thing with it you will get an update for the game the old overwatch is gonna switch to overwatch 2 if that makes any sense to you. source
The transition between Overwatch and Overwatch 2 has been a rocky road for players. We first had to come to terms with a sequel to the ongoing game, which felt odd on its own, only to be further confused as more details came out. Overwatch 2 would be free but also replace the original, meaning that even those who preferred the balance and systems of the original would have no choice but to upgrade. On top of that, Overwatch 2 would implement a new battle pass model for unlocks instead of the old system of loot boxes for cosmetics and all heroes being available for free.
By now, most players should be familiar with how battle pass systems work. However, due to this being brand new to Overwatch 2 and directly opposing how certain things worked in the previous game, it is leaving a lot of fans concerned, to say the least. To clear up all the questions Blizzard has left ambiguous or simply hidden, here is a full explanation for how the Overwatch 2 battle pass works.