Magic Resistance should not to be confused with Damage Reduction Vs. (DRVs).
Magic Resistance is the percent chance that a character will be completely unaffected by a spell. This resistance check is in addition to any Damage Reduction Vs. (DRVs) benefits that the character may have. To determine whether a character is affected by a spell, magic resistance is checked first. If successful, the character is unaffected by the spell in any way. If unsuccessful, then the DRVs check is made to determine the spell's effect.
Spells of a beneficial nature are not subject to magic resistance or DRVs checks for obvious reasons.
In addition, some spells are crafted in ways that do not allow for magic resistance. Example: Magic Darts can't be resisted
Note: A character that has Protected From 1st Level Spells will resist ALL 1st level spells. The same holds true for Protection From 2nd Level Spells etc. even if the spell is of a type that can't normally be resisted.
Damage Reduction Vs. (DRVs) Whenever a character is subjected to damage from a magical spell, there is a chance the character will not suffer the full effects of the magic. If a character is successful in their Damage Reduction Vs. (DRVs), the damage taken by that character is halved.
DRVs are expressed as a percent chance for success. Example: A character with a 20% DRVs Heat is hit by a Fire Ball and receives 20 points of damage. A check of DRVs Heat will automatically be made. If successful, the damage will be reduced by half, thus the character will only take 10 points of heat damage.
In some instances, the effect suffered by the character is an all or nothing deal; as with a Polymorph or Blindness spells. If the character is successful in DRVs Magic, the character is completely unaffected.
Some magical attacks require the character to DRVs Caster. This means the character must pit his ability to resist the magic against the spell caster's ability to cast it. Charm Foe spells are one such example. The character must DRVs Caster or be charmed by that spell caster.
From time to time an individual member of the party may have to DRVs some other attribute. For example; if the party steps on a trap, the characters may have to make a DRVs Agility or fall in. Therefore, good attribute scores are always of value, even if they do not seem all that important during character creation.