Refinement is just another word for processing. When food is processed or refined, a lot of the natural nutrients -- the good stuff your body needs -- are stripped out. What's left are empty calories that don't give you much nutritional benefit, like in white bread, for example.
So when it comes to food and carbs, refinement is a bad thing. Pick whole grains over refined grains such as white pasta, bread, or rice when you have the chance. Also, steer clear of too much table sugar and syrups that are added to food, like high-fructose corn syrup -- those are refined, too.