On a low level, it's total carbs minus fiber (which your body cannot convert into energy) minus sugar alcohols (as mentioned).
As far as if the example you mentioned is "good" or "bad"? That entirely depends.
On a high level, high glycemic index (and particularly high glycemic load) foods will generally spike your glucose levels rapidly when compared to low glycemic load foods which are generally characterized by more gradual blood glucose rises as low GI foods are digested slower.
There are many theories about what causes insulin resistance and type 2 diabetes, but it's hard not to see how foods that cause a sharp blood glucose spike probably aren't best for someone with type 2 diabetes.
Long story short, you will have to decide what is "Good or bad" for your body. Many people on this forum believe that all carbohydrates are bad for you. Personally, I think the answer is a heck of a lot more complicated than that.