Rarities are ways of classifying Items, mobs and so on

Items usually have these rarities:

• Common
• Uncommon
• Rare
• Epic
• Legendary
• Mythic

These are the common progressive rarities, each better than the last.

There is a few other rarities that might not be better or worse, and it's up to you to rank them! I repeat, these rarities might be BETTER or WORSE depending on many things:

• Unique (For Items, these mean custom unique stats)
• Runed (You can socket Runes in these to create a Runeword, which gives the item a lot more stats)

Some Runewords are meant for the early game, maybe they're easy to craft so new players have some way of deterministic gearing. Or they might be super endgame Items that are mega rare like certain Uniques.

Mobs have some additional rarities:

• Bosses
• Uber Bosses
• Summons