Talk:Quelaag's Furysword/@comment-69.116.240.165-20140811100958/@comment-5264386-20140811103015

They are the Parameter Bonuses of a weapon; that is, how much extra damage you get from your stats. Think about it this way: for instance, if you're able to lift more weight, then you're also able to exert more force when you smash a club down. That's pretty much how the paramter bonuses work; the higher your Strength, Dexterity, Intelligence and Faith are, the more damage weapons will do (of course, this depends on the type of weapons used).

Now, onto what the letters actually mean. In Dark Souls, there are six scaling ranges (from highest to lowest): S, A, B, C, D and E. As one would expect, a weapon with an S ranking in Dexterity will get more extra damage than one with an E ranking in Dexterity. However, these letters represent a range of scaling values, not just one singular value.

This explains why a +15 version of a weapon is better than a +10 version, regardless of whether it has the same scaling rank or not. You can find the exact ranges on this page. Finally, when you compare two weapons with the same scaling rank (let's say "C"), the weapon you're comparing to your equipped weapon may have a blue or red letter. The former means that it has better scaling, whilst the latter means that it scales less than your current weapon.

Anyway, hope this helps! :)