Tying up or restraining your consenting sexual partner.
Usually the restraining is done by the dom (dominant) and the sub (submissive) is the one restrained.
Sexually arousing for some, as the exchange of power is exciting, and the helplessness of being bound allows some people to really let go and enjoy themselves. Also, having complete control over a willing partner is very arousing. There are many reasons people enjoy this.
HAS NOTHING TO DO WITH VIOLENCE.
Bondage is often used in conjuction with punishment/pain play, but it is NOT the same thing!!!
He was obviously into bondage, so I tied him up and teased him mercilessly until he begged me to fuck him.