Season Passes differ between games, which is why they're generally a bit of a bunk idea; the typical thought is that they're supposed to include all of the DLC released for a game but in practice... well, in Borderlands 2, for example, there's quite a bit of content you'll still need to pay extra to get even if you do buy the Season Pass.
For Bioshock Infinite specifically, it includes the "Clash in the Clouds", which I believe is just some arena mode thing, and the two "Burial at Sea" story DLCs. EDIT: And BI only has one other piece of DLC, which is just a start-of-game boost sort of thing that you really don't need to bother with.