Pierce Points (PP) is pure damage point which can be obtained from (Fight & Wars - )Practice. PP points are added at the end of the damage calculation equaling the Total Points value and can be used for both, physical and energy hits. To better understand, look at the damage formula:
Total damage = (Weapon damage - Armor defense) + PP
PP damage is piercing and cannot be reduced by armor or equipment. More PP points collected, better advance against your enemy. These points can be obtained from practice, but only when you succeed. Total Points Value can be raised once every day, but keep in mind that if you skip one practice, your total will be decreased. (For details, check the practice section).
You can see your Total PP points an the Practice tab or at player overview:
PP points are useful for those who are fighting with stronger aliens or in arena. Each player can take his decision if is worth for it to practice or not.
No, you can't lose more PP points than you earn, min. is 0, max. is unlimited