Adventuring Trainer
An Adventuring Trainer is a Skills Trainer that can train your Adventuring skills. Some can only teach you basic skills, advanced skills and master skills.
Trainers found in the Outskirts areas can only teach you basic Adventurer skills.
Trainers found in the various NPC Town's can teach you basic and advanced Adventurer skills.
The Master Trainer can teach you basic, advanced and can teach you the most powerful of a specific Adventurer skill.