GM items are special items. They can only be found in loot.

Item modifiers improve various skills and stats on clothing, jewelry, armor and shields.

Pentagram pieces are special loot items. Completing pentagrams and turning them in at the appropriate NPC gives special Pentagram gear.

Protection modifiers give specific defensive bonuses against magic or physical damage.

Skill modifiers on items improve specific skills.

Weapon modifiers improve weapon speed, damage or grant extra stats.