Healing potions are mystical liquid sealed in glass vials that provide a set amount of invigoration. They often get lost in inventories, meaning they're never where you need them.
In the fight with the exploding skeletons, Torq grabbed his healing potion with the intent to use it, but was knocked unconscious before he could use it. The potion dropped from his hand and rolled into a corner. Orem used his mage hand to tip a drop of it into Torq's mouth.