Not sure what you mean by "passive", but you can add skills and talents to equipment purely with stats. As an example, adding "Target_FaceRipper" to the "Skills" field in a Weapon stat grants you that ability when equipped.
Active abilities are hotbar skills. You have to click a button or press a key to apply their effects.
Passive abilities are attributes, combat skills, civil skills, and talents. Once you have them, they apply their effects until you have them no longer.
Charms in Diablo II, for example, are passive abilities implemented as items. They are functionally the same as any other passive ability; you just use a different UI to manage them.
