When you hover your cursor over one of the buttons (bite, blow, rush) it will show you which of your opponent's moves is being blocked.
This is useful if you know your opponent has a certain attack skill, like a dragon with fire breath or a roc with lightning strike - you'll want to keep using Rush, to stop them using Bite and unleashing that powerful attack.
In the arena, hover over the beasts during battle and a list of their genes/skills will pop up, for reference. You could also check their profiles before entering battle, if you're cautious.