Kongs are a life saver for dogs if you need to leave them in a room or crate for long periods of time, or just to mentally stimulate them. Kongs can be filled with treats like in the pic, or just with the dogs (appropriately measured) regular meals. For dogs new to kongs, I would recommend only filling it up a third of the way with treats, and smear peanut butter around the opening but not over it.
Also, the 'tantalizer' part is actually supposed to be a hole to prevent pressure building up if you stuff your kongs to the max. Because if you tried to clean out a kong stuffed completely with, say, the kong paste, and filled that little hole, there's a chance it will plop all over you once you put a finger in. Physics, man. Of course, you can avoid that by knocking the kong against the side of a trash can or sink to dislodge the insides