Every Minecraft Bucket: Water, Lava, Milk and Mob Buckets

Quick answer

Craft a Bucket from 3 iron ingots in a V shape.
Empty buckets stack to 16. Full buckets don't stack.
Buckets carry water, lava, milk, powder snow and some small mobs like fish and axolotls.

The bucket is one of the most useful items in the game. Here's every kind of bucket and what each one is for.

Crafting

Put an iron ingot on the left and right of one row, and one in the middle of the row below. You get 1 bucket.

Bucket	How to fill it
Water bucket	Use an empty bucket on a water source
Lava bucket	Use an empty bucket on a lava source or a lava cauldron
Milk bucket	Use an empty bucket on a cow, mooshroom or goat
Powder snow bucket	Use an empty bucket on powder snow
Cod bucket	Use a water bucket on a cod
Salmon bucket	Use a water bucket on a salmon
Tropical fish bucket	Use a water bucket on a tropical fish
Pufferfish bucket	Use a water bucket on a pufferfish
Axolotl bucket	Use a water bucket on an axolotl
Tadpole bucket	Use a water bucket on a tadpole

Mob bucketsA bucketed mob travels as an item in your inventory. It's the easiest way to move an axolotl or tadpole to your base.

Water bucket: break your fall by placing water as you land, and use two to make an infinite water source.
Lava bucket: one of the longest lasting furnace fuels. You get the empty bucket back.
Milk bucket: drink it to clear all effects, or use it to bake a cake.
Powder snow bucket: build freezing traps for mobs.

Place carefullyA full bucket empties onto the side of the block you click. Look before you place lava.