Well, I am not an expert, but I have learned a lot from the South Beach Diet book.
Some foods have less carbs than others, and they also contain fiber which is good for you.
For example, plain old white bread contains a lot of carbs, and because of the way it is processed, very little fiber. It also has a very high glycemic count. Eating a slice of white bread is like putting a tablespoon or two of sugar in your mouth.
Whole grain bread, on the other hand, does contain carbs, but it also contains a lot of fiber, and therefore is much better for you.
Another example is oranges. Oranges contain carbs but some ways of eating them are better than others. If you drink orange juice you are getting all the carbs and sugars of several oranges at once, and your body doesn't have to use much energy to digest it. But, if you eat an orange itself, you get the pulp and your body has to work to digest it.
There are so many sites on the web that can explain much more to you. I'm still learning all about carbs and glycemic counts and fiber, etc, but I realize that with a little work and a little learning, I can eat a lot healthier than I have for most of my life.