Iron Ingot
Iron ingots are made from putting iron ore in the furnace.
As a Crafting Ingredient
You can use iron for the following:
Iron Helmet (5 pieces needed)
Iron Chestplate (8 pieces needed)
Iron Leggings (7 pieces needed)
Iron Boots (4 pieces needed)
Iron door (Like wooden doors except that they can't be opened by hand) (6 pieces)
Shear (used to chop down organic material easily, and collect cloth off sheep without killing them) (2 pieces)
Bucket (Used for storing lava, acid, water and milk then pouring out somewhere else later on) (3 pieces)
Block of iron (can be used as a building block, but also are excellent for storage. Since they stack to 64 and can be crafted back into iron, they are excellent if you have little storage space) (9 pieces)
Flint and steel (used to burn things!) (1 piece)
Iron Sword (Usable 251 times) (2 pieces)
Iron Pickaxe (can mine everything except obsidian) (3 pieces)
Iron Axe (3 pieces)
Iron Shovel (1 piece)
Iron Hoe (2 pieces)