Want ask some mechanic. (Resistance, Armor, Shred, Penetration

[Samseng Yik]

Played POE for 7 years.
Think LE not bad too, but got some question about the mechanic .

So let say I choose the ranger girl, "Throw Poison Bottle" skill as example.
This skill has passive like
"shred armor", "reduce poison resist", "Poson resist penetration"
How differently it work ? Do the game also has "Shred Poison Armor" ?

[Ayk-]

Shred armor reduces your enemies armor per stack. There is no such thing as "specific" armor.
The other two work as you would have guessed.
Keep in mind, armor only applies to hits. If you are playing damage over time build, not a hit build, negative armor on enemies won't increase your damage.
If you are playing a poison build, just focus on the other two stats, shred armor does not matter too much for you.

[Samseng Yik]

Understand, thanks.