What Is a Nebi?

If there's no Sharia before Adam, according to this definition, how can he be a Nebi? He has to be a Rasul, and the Qur'an said he's Nebi. So you guys seeing... and you know honestly, I asked this to some of the advanced students when I teach in Al-Mahreib,. And that is the panel of these simple questions. We just gloss over them from Sunday school, and we never think about them. Such a simple question. What is a Nebi and what is a Rasul? The more you know, the more you realize you don't know.