There are eight elemental properties, all of which are either effective or ineffective against each other. Using these elements in battle can be very usefull, but just remember that a lot of monsters can use them too. To use them, study the list below to understand which elemental properties to use on certain monsters.

Fire - Effective against Ice and Undead monsters.
Ice - Effective against Insects, Fire, Dragon-Type monsters, and large enemies.
Thunder - Effective against monsters near water.
Earth - Inaffective against Flying monsters.
Water - Effective against Fire monsters.
Wind - Effective against Flying monsters.
Holy - Effective against Shadow monsters.
Shadow - Effective against Holy monsters.

There's also a non-elemental property. The other properties have no special effect on it; they do regular damage.