It sounds as if your dog may be seriously unwell. Get him to a vet for assessment as soon as possible.
How old is the puppy? When was the last time the puppy ate?When was the last time the puppy drank?Is the puppy updated with vaccination? When was the last vaccination? Could the puppy have eaten anything or gotten into something that could be poisonous? Is there any other symptoms tired low energy change in bowel movements fever etc.? How long has the puppy been like this?You did not give any helpful information for anyone to really help? No matter what he needs to see a vet ASAP PLS DO NOT WAIT!!!!!!!!!!!!!To be honest it could be anything he needs a full examination from a vet it is not a good sign when puppies do not eat or drink and they need immediate help from a vet they could go down hill very fast when not drinking and could get dehydrated and can die .The puppy needs a vet.
It means he is very sick and needs to get to a vet as soon as possible. He might have something stuck inside his mouth or throat. I've also seem dogs salivate when they are in a lot of pain. It could be number of sicknesses that puppies get. No matter what it is, don't mess around with a puppy that won't eat or drink. You can lose them very fast. Take him to the vet.