Like the name suggests, they are unique, meaning that the odds that they will spawn more than once each game are nearly impossible, and they have fixed properties that stay the same regardless of when they spawn, but the same properties can go a few points up or down. Unique: These items are the most rare that can be dropped from monsters.As more items from the same set are equipped, more bonuses are given to the character, and when all set items have been gathered, a massive bonus is provided. Rare: Like magic items, except they have more properties.Magic items have a good chance of dropping and a player can increase that chance with other equipped items or charms, jewels and gems. Prefixes and suffixes determine what extra properties the item will have. They have a few extra properties to them chosen at random when the item spawns. Magic: The first items the player will come across of a higher quality are magic items.Superior: Superior items have improved Defense, Durability, Attack Rating, or enhanced Damage.Also, it is worthy to note that some uniques are better than runewords: it is not to say that all are better.
In function, the are like unique items, spawning with the same attributes from game to game. Rune Words: The most powerful items in the game are runewords.Both Armor and Weapons have their maximum durability degraded to, i.e. a low Javelin has One-Hand Damage: 1 to 3 rather than the normal One-Hand Damage: 1 to 5). Minimum damage is modified to 1 if it would be < 1 (e.g. Low Quality: Any low (Low Quality, Cracked, Crude, Damaged) Armor appears to have 75% of the normal defense (don't forget that normal defense varies), rounded down, and low Weapons do 75% of their normal damage (mindam, maxdam), rounded down.Some items, most notably equipable items, but also charms and jewels, can spawn in different quality levels. Quest Items: Items used during the various quests the player completes in the game.Potions: They increase Life, Mana, Stamina, provide resistances or can be thrown at monsters.Arrows and Bolts: Ammunition for Bows and Crossbows respectively.Tomes: Used to store scrolls, maximum 20 scrolls per tome.Scrolls: Used to identify items and to open town portals.They can be magical, rare and unique like regular items, and can provide powerful bonuses. Jewels: Similar to gems and runes, jewels are also inserted into socketed weapons.Charms: When held in your inventory, they can provide you with a bonus.Runes range from very weak to quite powerful, and if inserted correctly, they will yield a runeword. Runes: Like gems, these are inserted into weapons.Starting from the lowest: Chipped Gem, Flawed Gem, Gem, Flawless Gem and Perfect Gem. When inserted, they provide bonuses to the item. Gems: Precious stones that can be inserted into socketed weapons.Apart from weapons and armor which are listed below, there are several other item types the player will come upon. There are many kinds of items in Diablo II.