No rankers are normal people who don't know how to use Flow energy or Any other power, or they did not unlock their abilities yet.

F Rank --- F rankers do know how to use basic Flow techniques, but they don't have any unique Flow to use on their own.

C Rank ---- C-Rankers are similar to the F- Rankers in that they know basic Flow techniques, but the difference is that they have one unique Flow ability to use.

B Rank --- B- Rankers are people who know how to use their powers easily and quickly and have lots of experience using flow that's unique on their own, or they have advanced users of Flow Weapons.

A Rank --- A- Rankers are way advanced in controlling their Flow or any other power. They have a vast knowledge of how to use their Flow in almost any situation and have their unique flow.

S Rank --- S-Rankers are way more advanced in controlling their Flow or any powers than others. They have a vast knowledge of their unique abilities.

N Rank is a very rare rank to come up to from S-Rank. Only three people in the history of humanity have ever been an N-Rank; one is Leo. These guys have a vast knowledge of how to use Flow in every situation, And They have very strong powers.