question about hexing and weap stats

I was looking at a weapon and one of the abilities was "armor penetration +20% (chance: 20%)" so if i am reading it right the sword has a 20% chance to add 20% chance of breaking through armor? And this check happens every time the sword is swung? Seems crappy but do i understand it correctly?

Second question: what are hexes? I have tried wiki but it doesn't show anything. How do i know if a monster has a hex or what skills put hexes on monsters or if im hexed?

Thanks for all your help and putting up with my noob questions. Im just trying to understand how to best play the game.

Yes, the check happens every time a sword is swung, and yes it is crappy. Vampiric is a lot better.

Hexes are like enchantments, except bad insetad of good. All hex skills say they are hexes in the description and have a purple arrow pointing down on the picture. You know you are hexed if there is a hex picture in the upper left corner of your screen. You know an enemy is hexed if it has that little purple arrow on their health bar.

Actually the sundering check applies to skills only (at least, I'm pretty sure. Someone feel free to correct me if they know for sure).
Anyway, its a 20% chance of having 20% armor penatration, which will add a little bit more damage to every 5th swing or so. Statisically, sundering is terrible and most people who use it are too lazy to use vampiric and a second elemental weapon set. Vampiric weapons statisically do more damage then sundering and will heal you over time so long as you are constantly attacking and hit with attacks. If you are worried about the -1 health regen, just use two weapon sets (the F1 and F2 button) to switch to a non-vampiric weapon in between battles.

Condition increasing weapons are deccent in PvE depending on your build and zealous is also sweet.

The sundering from str is only on skill use, weapon sundering is with all swings, skill use or not