Well technically it's how well those kind of attacks are against that type of monster. So let's say there is a Beast type monster. It's element is beast and it has a low beast resistance (Just click F resistance to Anti Beast) Then there is a skill that does damage to beasts (Put Anti Beast *Checkmark*) and the skill will be very effective against the monster. Same goes with the rest of the elements. Still confused? Tell me and I'll put up a tutorial for you