Could someone explain exactly how resistances work?

[CroixRaoul]

I know what you're thinking, check the Wiki, but on the wiki it says (Todo: Add the mechanics and formulas behind resistances.) I understand that the bigger the number the less spells hit you, but does anyone know more about how it works?
For example, what does 45 magic resist mean? 45% chance to resist spells of that nature, or?