Bondage is one of the core areas of play for BDSM, and provides the ‘B' in "Bondage, Discipline, Sadism, Masochism".
Culturally, bondage comes from many different roots and many cultures. Japan has evolved highly complex and artistic forms of rope bondage called "shibari". Germany is famous for their latex or rubber bondage, and almost all cultures embrace the usage of leather, cuffs or other forms of restraint.
Some Masters or Mistresses like to indulge in complex games, or make artworks from a beautiful woman. However, bondage does not need to be complex or highly prepared and can be as gentle as silk scarves and candle light.
One of the most popular aspects of bondage is to allow the Master/ Mistress to dominate their slave. When bound, the slave can no longer object and must submit to their owner.