When a puppy is first born, their sense have not started working yet. Once they are two weeks old, their eyes open and other senses develop. During this stage they are not able to eliminate waste on their own and this must be stimulated by the mother. Because of this, puppies are completely dependent on their mother. They do a lot of sleeping during this phase and will only wake up to find their mother and feed. For more information, check out the below graphic.
Graphic created by Green Pet, a retailer of earth friendly dog products.