A stat passive is meant to be a direct enhancement to any one of your core stats, whatever you choose to make this apssive, it allows a character to increase by a "+" in one stat. With the intent to represent expertise in within said category. For example,

Strength (Before Passive): Superhuman

Strength (After Passive): Superhuman+

A narrative passive is meant to represent a unique trait, adapation, or defining charateristic which cannot be defined through the stat system. These ppassives help to reinforce a characters strengths that lie outside of combat. For example, a thief may have a narrative passive which naturally makes them better at stealth.