The Korean skin-care routine can involve anywhere from 10 to 30 products, including numerous steps to deliver each product onto the skin in just the right way. Most Americans are accustomed to the standard 3-step “cleanse, treat, moisturize” routine, and any attempts to incorporate the expansive Korean skin-care regimen can cause some confusion — particularly around step 3-ish: the essence.

Korean women start their skin ritual with a wash (or double wash), followed by a tone. Then, before the moisturizer stage, comes a litany of products that can be downright confusing to differentiate. The stage following cleansing is called the treatment stage, which in Korea can include serums, essences, boosters, concentrates, and ampoules. Though I knew I didn’t necessarily need to use all of these products, it was hard to know where to begin. So, I set out to find some answers.

Perhaps the biggest point of confusion is around serum and essence products. An essence is a highly enriched, lightweight formula to be applied to the entire face, while a serum is a concentration of nutrients to be applied for a specific purpose such as brightening, anti-aging, or to combat specific problem areas of the face like dark spots or acne.

True essences are programmed with the goal of enriching skin and preparing it for oncoming products. Essences are lighter than a moisturizer and more viscous than a toner. They should be absorbed into the skin immediately following toner application, when the skin is at its cleanest. Essences are applied in the same way as a serum: pumped or piped onto the fingertips and gently slapped or pressed into the face. Serums, on the other hand, tend to be more concentrated and are used to target a specific purpose, which is why they usually come in smaller quantities and with higher price tags.

That brings us to ampules and concentrates. These are usually heavy-duty, maximum dose concentrations that are used over 2 to 4 week periods for an extra boost of vitamins or concentrated nutrients. Ampoules are usually packaged for one-time use, and concentrates are generally single ingredient-centered extracts that come in tiny dropper vials. Finally, a booster is meant to prep and prime the face so that following products have maximum efficacy.

After testing the different products, I definitely wouldn’t find it necessary to use both a serum and an essence. Essences are unique to Korean makeup, and serums come in equally lightweight formulas. I’ve used many products out there formulated to nourish and prep your face — some are called serums, and others essences, but their effects were the same.

Regardless of how many steps you entertain adding to your routine, I’ve pulled together my favorite treatment products for your consideration. To keep it simple, they follow toner and precede moisturizer in the skin-care routine, and in function, they all aim to deposit nutrients into the skin. And, though I think one treatment product (serum, essence, concentrate, or ampoule) is sufficient, if you choose to layer, a general rule of thumb is to start from lightest in texture and work your way up.