Korean essence vs serum vs ampoule - what is the difference?

These categories overlap and naming is partly marketing, but generally: an essence is a lightweight, watery hydration/treatment step (e.g., COSRX snail essence) applied after toner; a serum is more concentrated and targets a concern (brightening, hydration, etc.); an ampoule is the most concentrated, often used as a short booster. You do not need all three — for hydration + brightening, a hydrating essence plus one vitamin-C or niacinamide serum is plenty. Apply thinnest to thickest: toner, essence, serum/ampoule, then moisturizer and SPF. Good starting picks: a hydrating essence (snail or HA), and a brightening serum (vitamin C in the morning, or niacinamide anytime). Layering more products rarely beats consistent use of a few good ones.

This is general information — an in-person consultation with a board-certified specialist is the only way to get advice tailored to your anatomy and goals.