Technically it is a breeder who is committed to improving the breed by making sure her/his puppies are wonderful examples of the breed.

They do that by health testing their dogs so they can reduce the likelihood of inherited diseases (some can't be eliminated entirely because they are caused by multiple genes). They carefully select the male dog who will sire the litter (same health tests). They should be showing (conformation) or trialing (obedience, bite sports, tracking, agility, etc.) their dogs and getting championships/titles on them - demonstrating that they are good candidates for breeding and can do the job(s) they were created to do.

Good breeders usually only have the mother on site. While once in a while they may also own the father, usually they don't. They usually only breed one litter a year ... possibly two, but that's about all any sane breeder can handle if they are also showing and trialing their dogs :)

They take names (not deposits) for future litters (you give a deposit once you are offered a puppy from a litter on the ground and you have accepted). They are likely to quiz you on your dog experience and what your home life is like and how familiar you are with dogs and specifically with their breed. So study up!

They socialize their puppies until they send them to their new homes.

That's just off the top of my head.