Wikia

An archetype is a group of cards that may follow at least one the following rules:

All cards in an archetype of cards must contain a common term (the name of the archetype) appearing in their OCG card names. Cards with the same words in their English names are not necessarily part of the same archetype (e.g. "Bolmeteus Samurai Dragon" is not a "Samurai" creature).
There should be at least one Support or Anti-support card relating to the archetype, that is, a card that references that term in their name, or mentions it by name in it's card effect or by "archetype creatures".
Members of the same archetype usually share a small number of similar factors such as Civilizations or Races.
Some archetypes can be a group of races with a similar naming theme.