It is quite obvious: ropes, cuffs, gags, blindfolds can enhance BDSM scenes. Restrictive devices make the sub feel more helpless and vulnerable, stimulating the submissive mindset.
Bondage is a form of sex play in which one person restrains another for sexual pleasure. There are also people who practice self bondage during masturbation.
People enjoy bondage for many different reasons. They may do it because they want to please their partner, they like the feeling of being out of control of their own pleasure, or they like the idea of being "used," even if it's in a consensual manner.
The "B" in BDSM, bondage is about allowing another person to be in control of your pleasure. Some people believe that the delayed gratification involved in bondage and other BDSM activities can make for a more powerful orgasm. Bondage can involve anything from handcuffs, blindfolds and basic restraints, to ropes, gags, sex furniture, and even cages.