Minecraft/Gunpowder

Gunpowder is used in crafting and in potion brewing.

Obtaining
Gunpowder is dropped from creepers and ghasts. You can also find gunpowder in most naturally generated chests.

Use
When brewed with potions, the potions turn into splash potions, which can be thrown to effect multiple players and/or monsters. This is good for negative potions like poison and slowness.