It's not about bondage, or domination. It's not about pain, or denial. It isn't about control or perversion.
To me it is about pushing boundaries, and finding out what you and your partner like. It is about mutual satisfaction and scratching the itches that we crave. It is about bonding over mutually shared interests and keeping the excitement in your relationship.
It's about what two (or more) people choose to do as long as no one gets hurt or used.