Hunters are NPCs That help you fight.
In order to have them spawn (Without cheating. Don't try to argue with me, single player commands.) you must talk to the guild master and click "Buy hunter".
If you have at least 1500 gold coins, the hunter will spawn and you will spend them.
The hunter will follow you around, teleporting if you get too far. (Similar to tamed ocelots/wolfs)
When you get near a hostile mob (Or an enderman, which is neutral) he will start attacking and kill it.
If the hunter kills it, he will not pick up any of the loot/gold coins and the mob will drop the same amount of items it normally would.
The player can choose whether he will use either a bow or sword by right clicking. (Sword is deafault.)
The sword will be an iron one, incabable of critical strikes, and will have unlimited durability.
The bow does not have to charge, cannot do critical strike, and will have unlimited arrows.
The hunter will not drop anything upon death, and its Health (AKA Hearts or HP) is unknown.
The only way it can be healed is by a priestess.