Full Dragon is the number one legendary and prestigous armour set in Runescape. The term full is player lingo and it means a complete melee armor set consisting of four parts: the full helm, platelegs, platebody and kiteshield. The different melee armour sets from lowest to highest are bronze, iron, steel, black, mithril, adamant, rune and dragon.
There is also the Barrows armour and the Granite armour, as well as Dragonhide armour for ranger - and various robes for mages. Neither of them really fit the full armour concept epitomized by bronze, iron, steel, black, mithril, adamant, rune and dragon. Black and Dragon can’t be smithed from metal bars so they must be found. Black can only be aquired from monster drops and Dragon only through Quests and from specific monster drops.
Please note that the full armour standard does not encompass just any helm, body, legs and shield - it refers to the full helm, platebody, the platelegs and kiteshield. The chainbody, medium helm, chainskirt and the square shield are not parts of the full armour. However, in the case of full dragon there was initially no platebody nor full helm and there still is no kiteshield available so therefore the full dragon came to consist of Dragon med helm, Dragon chainbody, Dragon platelegs and Dragon square shield. The Dragon full helm was released in mid 2007 and the Dragon platebody in 2008 and the full Dragon is now closer to what it should be: Dragon full helm, Dragon platebody, the Dragon platelegs and Dragon square shield.