Bondage is a type of play that some grown-ups do sometimes. It means tying each other up, but it's not like being punished or anything bad. They like to do it because it makes them feel good and loved. They might use soft ropes or leather straps to tie each other's hands or feet or bodies so they can't move much. People who do this often agree on safe words so they can stop if it becomes uncomfortable for them. It's like a game but with grown-up rules.