All melee attacks and most spells have a guranteed hit.
Arrows and some projectile spells (I think Stone Daggers is one) have a minor homing property, so they can be dodged by simply moving out of its way if you cared to.
Otherwise there are some skills that grant you a chance to dodge, such as Escape, in if it suceeds you'll dodge whatever it says you can dodge (melee, spells, etc).