Nail prep is everything that happens before colour: gently pushing back and tidying the cuticle area, removing the invisible layer of dead tissue on the plate, shaping, buffing the shine off the surface, and dehydrating and pH-balancing the nail so product can bond. It is the least photogenic part of any appointment and the most predictive — the majority of early lifting and week-one failures trace back to rushed or skipped prep, not to the product or your lifestyle.
Good prep is thorough but conservative: the nail plate should be cleaned and de-shined, never thinned. A tech who spends unhurried minutes on prep before opening a single colour bottle is showing you exactly the habit that will keep your sets on for three weeks at a time.