There are many but in the first arc this is going to be the main ones
System users - can level up endlessly by training learning new things or getting new accoplishment -chosen by doing some accomplishment getting an rare item doing impossible feat - each level is insanely hard to get and each level will record your feat
But each system user is based on which server they are on and each server has an administrator records your feat but system user has to balance the world or they'll get Thier status as a system user removed
Non system users - they are not bound to anything-
I'll add more in the future