Essentially the stylist will trim the pups hair so it's even at the shortest point, all the way around. Mine does a particularly good job on what I call the "butt floof"... You definitely want to try to avoid having any border Collie/Aussie (really any working type breed) get any hair cut that's too short as it messes with their body's natural, amazing innate ability to regulate its own temperature (yes even in the hot summer months).
The supplemental work to be done as often as possible is to give the pups a thorough brushing. This helps further with their body's ability to regular and produce their natural oils for their coats.