well i suppose ordinary pencils are the graphite ones tht range from 2H to 2B but the full range can go from 9H to 9B. Graphite pencils are nice to use and probabley the easiest but if u start to use the darker pencils {2b to9b} you will start to see a sheen develope when u hold it at certain angles but they are very good at keeping there point.
Carbon pencils are a much darker matt black colour and so far the only ones i have seen range from B to 6B. Whats nice about them is that you dont get a sheen from them and u can get a nice feeling for depth with them, on the down side they are harder to blend and they are softer so lose there point easier and some people dont like the feeling when u draw with them but i think they are great so its each to there own, just need to have ago with them im glad i did. the best ones i have found is Wolff's Carbon Pencils. hope this helps