A Ranged pure in Runescape is a type of Combat pure who specialises mostly in the Ranged skill and focuses on raising it to high levels. They are mostly found in the P2P worlds, where they are considered to be most effective.
A Range pure relies on the basic idea that increasing Ranged is equal to increasing the two sub-skills Ranged Attack and Ranged Strength. Thus, a Ranger only has to increase one skill, where a Melee increases both Attack and Strength.
A Ranged pure, therefore, has a lesser Combat Level than a Melee, with arguably the same attack statistics. Most Ranged pures, except the Ranged Tank, concentrate on having their Defence level as 1, thus having a lower Combat Level.