From Minecraft Wiki
Iron may refer to:
Iron Ore − an ore found underground, and the item obtained by mining it.
Iron Ingot − an item created by smelting Iron ore, used for crafting.
Iron Nugget − an item obtained by smelting tools, weapons, or armor in a furnace.
Block of Iron − a block created by crafting 9 Iron ingots, used for compact Iron storage, for decoration, and to create Iron Golems.
Iron Bars − a block made of Iron that function exactly like glass panes.
Iron Golem − a neutral mob which targets neutral or hostile mobs to protect villagers.