The first one is "Dunwall City Trials," which adds 10 "challenge maps" for players that includes an arena to battle waves of enemies, "a gravity-defying run of drop assassinations," and timed races. A whole new batch of Achievements and Trophies will also accompany the DLC along with a global online leaderboard, so you can see how well you rank against others.
The second and third DLC packs will be more story-focused, with Daud as the main lead in the second DLC.
Dunwall City Trials will be available for $5 (400 MSP) in December. We'll have to wait until the other packs are closer to release to find out how much they will cost.