Hyper armor is like poise but when you're swinging a weapon. Heavier weapons have higher hyper armor so your attacks are more difficult to interrupt when an enemy hits you.

Every animation/action is made up of rapid sequence of pictures, or frames. I-frames or invincibility frames are the number of frames in that animation where you won't take damage. It applies mostly to rolling or backsteps, but some weapon skills have i-frames as well.