Weapon Triangle
Sword: strong vs. Axe, weak vs. Spear
Spear : strong vs. Sword, weak vs. Axe
Axe : strong vs. Spear, weak vs. Sword
Anima : strong vs Light, weak vs. Dark
Dark : strong vs Anima, weak vs. Light
Light : strong vs Dark, weak vs. Anima

Note: some weapons reverse the weapon triangle

Using the Weapon Triangle effectivly can give you an advantage in battle.