Instance what does it mean?

What does instance mean? Standing still or using a specific skill that says stance in the tittle?

If I use a shield with instance mod when does it apply?

a skill that is listed as a stance will give you the bonus

instance = in a stance. Which in any of the "stance" skills like Tiger's fury, Sprint, or Balanced Stand.

I really have to say that at this particular point, proper typing/English is a neccessity. "Instance" is a very, very different thing that "In stance," and to assure you're getting your question answered, please be careful as to what you say.

I think "In stance" has been covered thoroughly, meaning while your character is in a stance X effect will be in place.

"Instance," however, hasn't been touched upon, since it seems like that's not what the original poster meant. Just in case, instance refers to the unique copy of an explorable map that is created for you and your party when you leave town or enter a mission.