These are two of many keywords that will be used
Sturdy – means in the case of armour and other situations, if it’s Sturdy, it always happens or it always works.
Flimsy – means it only happens on a 4+
For example, if you have one Sturdy armour, then you reduce the damage you take by one on every attack, but if you have one Flimsy armour, then you reduce every damage by one on a 4+
In armour this will be written as 1S (1 sturdy armour) or 1F (1 flimsy armour) or both 1S1F (1 sturdy and 1 flimsy armour – meaning it auto blocks 1 damage, and blocks a 2nd damage on a 4+)
Piercing – Piercing damage ignores armour. If a weapon has 2 piercing, it will be written like this: 2P. Sometimes only some of the damage is piercing, so it will be written as 2+1P
If a weapon has 2+1P, then 2 of the damage is treated as normal, but 1 of the damage is piercing and ignores all armour.