A hostage is a prisoner taken by kidnappers and held until the kidnappers get whatever they’re asking for. If you refuse to empty the litter box, your roommate might take your cat as a hostage until you clean it.
When hostages are taken, the hostage-takers often ask for ransom, which is money paid for the hostages. The funny thing about the movie Dog Day Afternoon is that when the bank robbers take hostages, the hostages don’t really want to leave because they sympathize with the robbers. People who take hostages might have other demands too. Unfortunately, hostages are not just in the movies, they’re abducted in real life for political and personal reasons.