Any kind of “kink” is deficult to explain to anyone not into it. Even within BDSM, there are almost as many variations as practitioners. Confined to just the spanking topic, it can vary from barely a tap with the bare hand (as far as I would ever deliver) on up to industrial-strength flogging.
When my lady was “riding cowgirl”, she’d give the signal when ready and a few light swats on the bottom would send her over the edge. We did this as part of an act of love, intensifying her pleasure.
There was no “power trip” involved and certainly nothing to do with anger or domination (some do get off on domination power exchanges, I’m not criticizing them as long as there is mutual consent). I have friends who are into much rougher play. I personally can’t get my head around it, but that’s my problem. It’s analagous, I suppose, to how much and what kind of spices you like in your food.
Our relationship was far more than “just sex”. Sex was one expression of our deep love. Any form of stimulation that improved the quality or intensity of that expression was an additional gift we gave each other and came from that love.