Elemental Attack vs. Resistance

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Suppose I hit someone with e.g. a Fire Brand weapon and they have fire resistance. Does the fire resistance negate any of the "normal" damage (i.e. strength + weapon damage value + 2d6) or does the fire resistance negate only the special fire effect of the weapon? Is there additional normal damage caused if the unit has no resistance (or a susceptibility) to fire, or just the effect of being ignited?

I guess I just dont understand the operation of elemental weapons vs. resistances very well. Thanks in advance