Minecraft wiki entry for Time-saving_tips, associated text: Once you are able to brew them, potions are an enormous time-saver in many different ways. Potions of Healing and Regeneration save you having to wait so long to heal; Potions of Swiftness allows you to move long distances rapidly. A splash Potion of Harming allows you to instantly kill large numbers of mobs in a mob trap, making collecting experience much quicker and easier. Depending on the mob, or the design of the mob trap, you may need to use splash Potions of Poison first, to weaken the mobs, and possibly Splash Potions of Healing if you need to kill undead mobs (and heal yourself at the same time).