The protection and resistance section lists the levels of protection or resistance against various attacks. The values derive from natural abilities as well as armor and spells that are in effect. The 0% level is what an unclothed human would have. It is unusual, but entirely possible to go below 0%. Exotic monsters can have a heightened vulnerability to fire, acid or otherwise. Certain magicks can also make one particularly vulnerable to a specific kind of attack.
Except for magic resistance, they all reduce (or increase, in the case of a negative value) the amount of damage received. A 50% level of protection will halve the damage taken form a corresponding attack. Magic resistance, as well as poison and disease resistance reduce the chance of being affected at all. The latter two can also reduce the damage you take from that poison or disease (if applicable).
Resistances acquired from different sources always complement one another, but their values can not simply be added together. Let’s say you are wearing the highly prized dragon scale mail, that gives you 70% fire resistance. Then, you find a magical ring that offers 40% fire resistance. Together they will confer 82% resistance to you. (The ring only blocks 40% of the 30% that the dragon scales let through. 40% of 30% is 12% of the original blast. 70% + 12% is 82%)
A few, very rare, attack forms bypass all the mentioned types of protection, but you can still shield yourself from them. Some of these attacks, like the harpy's scream or the basilisk's gaze, work on your senses. Disabling those senses, either by magic or tool (earplugs, blindfolds), will grant you immunity to these horrors. Of course, being blind and deaf has its drawbacks, too!
High willpower can also offer protection against many such attacks, as it allows the target to resist their mind-affecting results.