BDSM stands for Bondage Discipline (or Dominance) Sadism and Masochism. It is a type of sexual activity that involves BDSM elements like physical power exchange, roleplay and ageplay, or kink activities like spanking, binding and tying up. So basically, BDSM is when one partner has a type of power or control over the other partner (sometimes both partners do). In culture and media, BDSM has become more mainstream in recent years and some movies, shows, and books feature BDSM as part of their story. For example, the popular movie "Fifty Shades of Grey" is about a BDSM relationship between two people. Some people choose to engage in BDSM activities because it can provide an exciting and thrilling sexual experience, while others may find it therapeutic and emotionally satisfying. And, of course, some couples just enjoy it for the fun.