Armor is made using either leather, iron ingots, gold or diamonds. A full set of armor requires 24 of those items. There’s a fifth type of armor, chainmail armor, which is made using fire blocks. This armor cannot be obtained in game unless you’re in creative mode or if you use mods.
Some armor pieces can also be found in chests or as drops from monsters. Zombies have a chance of dropping an iron helmet and zombie pigmen have a chance of dropping a golden helmet. All pieces of iron armor can be found in chests in villages and strongholds.
Like tools and swords, armor has limited durability. This durability is not equal for all pieces made out of the same material. Diamond armor, like diamond tools, has the highest durability. Any durability loss does not affect the armor rating off that item.
Armor can also be repaired in the same way as tools. By simply placing 2 pieces of armor of the same type and material in a crafting interface, a new piece of the same armor will be created with the durability of the old ones added together, plus 10%. Note that any enchantments on the old armor pieces will not be transferred to the new piece.
Armor can be enchanted with various different power enhancing abilities. Most armor pieces have the same enchantments, though there are a few pieces which have their own enchantments as well. Like feather falling on boots.
Armor doesn’t reduce all the damage types a player can take. However, some enchantments will reduce or postpone effects of some types of damages, like suffocation or fall damage.