The lowest rank on the forum is Academy Student / E-rank Nin.

Once you have mastered the needed skills, you're able to graduate and become an actual ninja. You'll get promoted to Genin / D-rank Nin when you're able to show your RP skills in the Academy.

Once the Genin has successfully undertaken three missions, they can be sponsored by their Jounin sensei for the Chuunin Exam. The Chuunin is the basic journeyman ninja of the village. These ninja can become field doctors or teachers. They were formerly Genin who were promoted for displaying excellent intelligence, strategy and combat skills in the Chuunin Exam. Chuunin have the equivalent rank of military captain, exhibiting strong stamina, knowledge and inner wisdom. You'll show your battle skills in the Chuunin Exams and get promoted to Chuunin / C-rank Nin.

Chuunins who are specialized in something can gain the rank of Special Jounin / B-rank Nin. Special Jounin are ninjas who have gained high Jounin-level skills in one area of ninja arts. You will get promoted to this rank when your kage thinks you're ready.

The rank above Special Jounin is Jounin. You'll enter the Jounin Exams and show us what you got. You'll get promoted to Jounin / A-rank Nin.

When you're the Leader of a Hidden Village you'll get promoted to Kage / S-rank. I know that there aren't enough Villages for everyone so when you prove to us that you're good enough ( RP correctly and stuff like that ) you'll get promoted to Sannin / S-rank.