Dungeoneering is a skill that consists of killing NPC's for tokens and experience which can be used at the Dungeoneering store located ::home. The Dungeoneering skill ranges from levels 1 - 99.
To begin this skill, you will want to visit the More Skills Teleport in your Magic Spellbook. Make sure you bring armour, weapons and food that will help you attack/defend the NPC's. You will receive more XP and tokens depending on which monster you attack.
The achievement of the dungeoneering skill is getting a skill point and a 99 in that category. You're then rewarded with the Dungeoneering cape and the skillcape emote.