A smack is normally somewhere on the body besides the face. It could be on the arm or leg.
A slap is with the palm of the hand on to the face.
A spank is normally with the palm of the hand on the buttocks or back of the thighs. Some people spank with a belt, wooden spoon, a cane, or a slipper.
A spanking that leaves a bruises or causes even a little bit of bleeding is considered a beating
If any of the above is towards a child in Australia, it is classed as child abuse.