Very broadly, quests come in two categories. There is the external quest, until recently engaged upon almost exclusively by men. Here the protagonist of a tale embarks upon a search – likely picking up Plot Coupons along the way – for something important to his survival or the survival of the Land for which he is or will be responsible, travels beyond the fields we know into the place where he will be tested and found worthing of winning the prize, accomplishes this goal, returns home with the desired object, or partner, or knowledge. The earliest external quest tale in Western literature, Homer's Odyssey (circa 850BC), is one of the first sustained narratives to have been conceived anywhere; and remains one of the finest. It underlies much of the quest literature of the Western world and much modern Genre Fantasy.
Second, there is the internal quest, in which females may participate more equally. Here the protagonist, whose goal is (broadly) self-knowledge, embarks upon an internal search, engages upon a Rite of Passage and returns to the world as an integrated person, a Magus, or a Shaman, or ... Dante's The Divine Comedy (1472), John Bunyan's The Pilgrim's Progress (1678-1679) and Lewis Carroll's Alice's Adventures in Wonderland (1865) are, at their various levels of seriousness, examples of the internal quest.
There are also quests which consciously join both elements, fantasies where full self-Recognition combines with the gaining of an external goal in a tale whose various elements interweave, generating a sense of full Story. In J R R Tolkien's The Lord of the Rings (1954-1955) Frodo's quest is double in this sense, and Stephen R Donaldson's Chronicles of Thomas Covenant the Unbeliever is a recent model for this attempt at integration.
Quests are sequential, suspenseful, event- and goal-oriented; they normally reach a conclusion (even the Accursed Wanderer's search for quietus is often rewarded, if only with death; and more than one tale of the Wandering Jew and the Flying Dutchman provide ultimate solace); those who oppose the successful conclusion of a quest – from the Knight of the Doleful Countenance to the Dark Lord – can often be best understood as mere symbols of opposition; and quests require an identifiable protagonist – from Ugly Duckling to Childe to culture hero – plus, usually, an accumulating mass of Companions to strengthen and complicate the action. Quests are therefore basic to the telling of Story; as fantasy as a genre is inherently tied to Story, it is not surprising that almost all modern fantasy texts are built around, or incorporate, a quest.
Quests are less frequent in Supernatural Fiction, whose protagonists tend to react to transgressive circumstances rather than explore new territory, though the Magus figures often found in supernatural fiction and Horror are often described as embarked upon foredoomed quests. [JC]