What it means is that your skill in Dodge is the determinant of your character's armour class. You won't notice any abrupt movement of viewpoint as the character dodges, or anything like that, but it's just as effective as ordinary armour in minimising the amount of damage your character takes. Dodge instead of armour has benefits and drawbacks. One benefit is that it never loses effectiveness by being broken. However, this is counterbalanced by the fact that you can't give your dodge ability a secondary benefit (fire resistance, say), and also if your character gets knocked out or paralyzed, his armour class drops a long, long way.
