Puppy pads are urine catchers that can save your hardwood and carpets from stains and wet spots left by a pee-prone pooch. They're useful for housebreaking a puppy or for a dog that just can't hold it in. Some puppy pads are laced with an attractant for enticing your dog, but in many cases the attraction is purely psychological.
Some puppy pads have a subtle scent that attracts dogs and makes them want to use them. You may not be able to pick up on the odor, but your dog's sensitive schnoz can. While they vary, scents may include an aroma like grass -- these are useful for housebreaking puppies, because they learn inside and out that peeing where they smell grass is positive. Ammonia is another regular scent, as dogs like to urinate where they detect ammonia; this is why you should never clean dog urine with an ammonia-based cleaning product.
Pheromones and Marking
When your dog goes to the bathroom, he doesn't just leave behind a wet spot and a smell -- he leaves behind pheromones, the hormonal chemicals that dogs use to identify one another. Territorial marking leaves behind both a unique smell and these pheromones; when your dog detects another dog's pheromones, he may want to do his business there. Dogs like to go to the bathroom where other dogs have already gone, so if your dog detects pheromones in the puppy pad, he may want to do his business there.
Not all puppy pads are specially treated with chemicals and scents, but that doesn't mean they aren't alluring to a dog. If you train your dog to use the puppy pad, he'll develop a strong psychological attraction to using it for his bathroom habits, even if there's no intrinsic attractant. Monitor your dog's behavior indoors, and when he uses the pad, lavish him with praise. If you catch him peeing elsewhere, stop him and direct him to the pad, then reward him for finishing there.
Using Pads Sparingly
Whether or not your puppy pads are treated with attractants, you shouldn't necessarily use them as your dog's only bathroom outlet. Peeing indoors isn't in a dog's instinct, for one thing; allowing him to go whenever or wherever he wants deprives your dog of the discipline he needs and structure he craves. While you can leave puppy pads out all the time in case of accidents or for long periods left alone, your dog should be getting regular, scheduled walks during which he can eliminate outside.