Someone once told me in game that them being a Duergar meant they would be resistant to magic weapons and have damage reduction vs them.
Is it true for all those races and is it like protection, 25% damage reduction vs magic weapons?
Thank you in advance for replies.

That will show how much resistance or vulnerability your class has against various damage types (whether from melee attacks, skills, spells or supplications).

I will try it as I guess you are saying it works for all resistances.

Fire, cold, lightning, acid, energy

Does resist magic give a bonus to things like - resisting sleep spell, or other spells which are "saveable" I know it reduces damage from elemental sources but I've always been curious if there is a bonus to resisting non-damage spells.

...no