Kittens are very helpless at this age, but the mother cat instinctively knows their needs. She feeds them, keeps them close by for warmth, bathes them with her rough tongue, which also stimulates their digestion and helps them urinate and defecate. Mother cats are very protective of their little ones, and will move them to another location if humans intrude too much into the nest.
Provided the mother has been vaccinated, or has natural immunity, the kittens will receive this same immunity for the first 24-48 hours through her colustrum, and it will last until they are old enough to get their "kitten shots."
Newborns will weigh an average of 3.5 ounces at birth and may double their weight by the end of the first week. They are simply little food processing factories at this point, and their only activities are nursing, sleeping, and passing waste. There is very little social interaction at this age, other than competing for their favorite nipple, where they will suckle while kneading with their tiny paws.