Number holder

Numbers Possessed
Numbers Possessed are people who have been infected with Numbers cards. Numbers can have varying control over people, either by increasing their already present emotions (As in the case with Tokunosuke Omoteura) to actually controlling and manipulating there mind (As with Fuya Okudaira). Some Numbers Possessed wish to gain more Numbers (Number 20's holder, Kaio, and Rikuo.) Although this has not present with all Numbers Possessed.

Numbers Holder
A Numbers Holder is a person who is immune to the corrupting effects of Numbers, but has no way of taking another person's Number. In this case it refers to someone who either borrowed another person's "Numbers" or previously had one and now uses a method to defeat them instead. Numbers Holders seem to gain their immunity by having a large amount of will (Tetsuo wishing to save Yuma and Shark trying to protect Yuma's Key). It is unknown if there are any Number Holders who have not taken their Number from someone else.

Numbers Hunter
A Numbers Hunter is a person who collects "Number" cards for one reason or another. Kaito Tenjo claimed himself to be a Numbers Hunter, being the only one, but later he identified Yuma as a Number Hunter (Yuma most likely doesn't see himself as a Numbers Hunter, but he technically is one.), making it an official term. Numbers Hunters have ways of detecting when a Number holder appears, and a method to take away that Number when they defeat it. Numbers possessed and Numbers Holders shouldn't be considered Numbers Hunters