You have learned how to make your healing potions work upon impact. Your Health I, II, and III potions gain the thrown property. Upon a hit, the creature regains hit points as if they had consumed the potion of healing.
At 5th tier, you have improved your throwing arm and your area of effect for health potions. You now have a range of 60 ft, and can heal all creatures within 5 ft of the target for half the roll.