Medical Spas (such as Nova) provide advanced body/skin treatment and rejuvenation that require trained professionals and licensing for each specific procedure.
Salons, however are leaning more towards beauty and cosmetics that are more simple to preform and do not require special certification and medical staff overseeing treatments.
Medical Spas are also known for using very expensive machines in their services such as Lasers, HydraFacial and Microneedling equipment.
Some medical spas may choose to provide additional services that salons have as primary.