Heroes of Might and Magic V [Game Discussion]

Map editor terms. There are minor, major, and relic artifacts. Minor artifacts are considered the weakest and are always plentiful.

Actually, these aren't just map editor terms. They are also frequently used in the game.
1) Minor (small) - the weakest artifacts. Usually found frequently.
2) Major (medium) - medium strength. Not uncommon.
3) Relics - the strongest artifacts. Usually rare.

You can see what belongs to what here:
http://heroes.ag.ru/heroes5/artefacts/all/

You can also pay attention to the names of the artifacts; they differ in color: