Punishment is quite different from an erotic experience. For instance, I can receive an otk, that is meant to turn me on, especially when She uses her hand or a light paddle. Which is accompanied by caressing my body with Her fingertips and softly manipulating my cock and balls.

A punishment spanking is done with a heavier implement, such as a wooden paddle, which leaves angry red marks and some bruises. That is also accompanied by slaps to my cock and balls.

An erotic spanking leaves me with a raging hard-on. A punishment spanking leaves with a limp dick, a very sore bottom. I can remember one spanking that actually made my butt-cheeks go numb.

It's important that the Dom or Domme lets the sub know why he or she is being punished. Reward for complying to a Master or Mistress's wishes is very important to the psyche of the sub.