|The quality of an object reflects its general workmanship, primarily how well it will hold up to damage when placed under stress (say, the impact of weapons and armor in combat). Additionally, quality can affect how well the item works for its intended purpose.|
In particular, the quality of the weapon will cap the skill rolls made with said weapon. For example, an average quality weapon caps the weapon skill at 60. This is not the same as other stat caps in that it doesn't actually cap your skill: what it caps are your skill rolls. So someone with a 75 skill wielding a weapon with a cap of 60 will still be more effective in combat than someone with a skill of 60. The skill cap also only affects the weapon skill, not the attack or defense skill (e.g. swing, thrust, parry).