Armor is a percent of damage that is mitigated when an armored vehicle takes damage from a certain direction. Incoming damage is reduced by the listed percentage values. For example, damage dealt to the rear armor of tanks is more effective. C4, Tank mines, and Anti-Vehicle grenades ignore armor. The direction used in the calculation is based on the position of the player dealing the damage, not which part of the recipient's vehicle is hit.
Damage resistance is a value that can either decrease or increase incoming damage from various types of weapons. A resistance of 100% means the vehicle is not affected at all. A positive number means incoming damage is reduced by that percent. A negative number means incoming damage is multiplied by that percent, dealing extra damage. Infantry have 0% resistance to all damage types, meaning they take normal damage from everything.