In a dog show, judges familiar with specific dog breeds evaluate individual dogs for how well they conform to published breed standards, hence the more accurate term is conformation show (or, sometimes, breed show).
"Dog show" is often used by the general public to refer to any event involving dogs, such as dog sports, but in the dog world it more specifically refers to conformation competitions.
Handlers set up their dogs for judging so that their stance is perfect when the judge views them.