If you know the meaning of the word prototype, then you can understand the word archetype. Archetypes are models or patterns that authors use to create original characters.
In 1919, the Swiss psychiatrist Carl Jung began promoting the existence of archetypes, although he actually gained inspiration from Plato. Jung named five main archetypes: anima, animus, self, shadow, and persona.
In literature, we have several main archetypes (although there can be many more than this):
- Great Mother
- Wise Old Man/Sage
Let's examine the hero archetype as an example. The hero's traits include the following (although there are others):
- Unusual circumstances of birth (in danger, born into royalty, orphaned)
- Leaves family/land and lives with others
- A traumatic event leads to an adventure or quest
- Possesses a weapon that only he can wield
- Has supernatural assistance
Believe it or not, many characters throughout literature meet this basic archetype. Consider Luke Skywalker (I'm assuming here that you've seen Star Wars a zillion times and I'm not ruining plot points for you). Luke's birth is hidden, and his mother dies shortly thereafter. He leaves his family to go with Obi-Wan (arguably their deaths are the traumatic event leading him to his quest). He has a lightsaber, and he has the "supernatural assistance" of the Force.
To provide another example, what about Aragorn from Lord of the Rings? He was born into royalty, but left his home to become a Ranger. Only he can wield Isildur's sword to gain supernatural assistance.
Still not convinced? Try Eragon from the Inheritance cycle. Eragon's mother abandons him to his uncle at birth. When his uncle is killed (traumatic event), he begins his adventure, wielding his supernatural weapons (dragon/magic).
Each man has his own character traits and flaws, his own personality, and his own appearance, but at their most basic, they are the same character--the same archetype.