Kongs are cone-shaped toys made of tough rubber that can be filled with food and frozen. Toppls are interlocking toys that can be used with dry treats, or stuffed like Kongs.
Your dog relaxes when he has something to chew on, and settles down after eating. Frozen Kongs (or Toppls) take longer to eat, giving your dog more time to relax. This also will gives the dog something to do when the owners are away. Dogs often sleep after eating, so the benefits of a frozen stuffed Kong are doubled.