Combat in FK generally operates on the principles of the d20 ruleset,
outlined online at http://www.d20srd.org. For those unfamiliar with these
rules (which are similar to those used in most dice-based role playing games
involving a 20-sided die roll to determine a hit), here are a few fundamental
features thereof:
Your opponent can be easier or harder to hit. This is characterized by their
Armour Class, or AC. The higher the AC, the harder they are to hit. When you
attack, you roll a 20-sided die. On a natural 20, you will always hit,
regardless of your opponent's AC. Otherwise, your die roll is modified by a
variety of factors and compared with your opponent's AC. If you beat the AC
score, you hit your target. In rare instances, you can connect with a
critical hit, which does additional damage and may even sever a part of
the body.
If you hit an opponent, you will generally do them harm in proportion to the
weapon you are using. Some creatures are resistant to certain types of
damage, and will only be hurt by inflicting sufficient damage of that type in
one fell swoop. See Resistances and Damage Reduction.