If the player puts certain combinations of Runes in the correct order into an item with exactly that number of sockets and of the correct item type, the item's name will change into a "unique" name, displayed in gold, and the item will acquire extra powers, depending on the "rune word" that was used. The benefits of using a Rune Word is that you can make the Rune Word's magical bonuses apply to any type of item allowed with the proper number of sockets. You could, for example, use an Elite Socketed sword or an Exceptional Socketed sword, and you can also pick which type of sword is used. Uniques, in comparison, use the same item type such as short sword, and are always the same quality (Normal/Exceptional/Elite). You can continue to find better Socketed weapons or armor and, with the proper Runes, continue to have this Rune Word bonus applied to better and better Socketed items as you find them.
Rune Words are an advanced feature for experienced users. However, anyone can create a Rune Word if they take the time to read/learn enough about them to assemble the Rune Words properly.
Rune Word Rules
Required Item Types for Formulae
Make sure you read this so you'll use the right items.
Body Armor = Any armor that is worn on your chest and not any type of other armor such as boots, helms, gloves, etc.Keep in mind when experimenting with unknown Rune Words that you must be prepared to accept the loss of your Runes if the formula does not work. Rune Words must be inserted into the correct item for the formula in the correct order. Blizzard cannot restore lost items for any reason including due to your failure to properly create a Rune Word. Rune Word failures are caused by using the wrong items, Runes, or Rune order. A few times the formula has been listed wrong on the following pages, but most (99%) of reported errors are caused by failure to understand the formula. The following formulae on these pages may contain errors, including listing the wrong formulas. Be sure you read all of this page including the bottom page notes for complete information.
Helms = Any armor that is worn on the head, including helms, Barbarian Helms, Druid Pelts, and Circlets.
Shield = Any armor that can be used to block, including shields, Necromancer Shrunken Heads, and Paladin Shields.
Clubs = Club, Spiked Club, and Exceptional/Elite versions.
Hammers = War Hammer, Maul, Great Maul, and Exceptional/Elite versions. These will not work in mace recipes even though they are listed on the mace page.
Maces = Mace, Morning Star, Flail, and Exceptional/Elite versions. This does not include any other types of Maces. Make sure you read about Hammers above. They are not "maces" in the case of Runewords.
Melee Weapons = Most weapons that aren't ranged such as a Sword or Hammer. A Bow or Crossbow is a ranged weapon and is not in this category. Sorceress Orbs are not considered Melee Weapons. Melee Weapons: Hand-to-Hand, Blunt, Combo Weapon, Polearm, Spear, Knife, Sword, Axe. Hammers (see above) are considered Blunt weapons, and will not work in Melee Weapon recipes, even though they technically are a melee weapon. This includes Clubs, Hammers, Maces, Staves and Rods which are excluded from Melee Weapons.
Missile Weapons = Bows and Crossbows.
Weapons = Melee Weapons, Missile Weapons, Orbs.
Scepters = Scepter, Grand Scepter, War Scepter, and Exceptional/Elite versions.
Staves - Mean Staves and not other items that are Staff class weapons like Wands.