You are not alone in having no earthly idea what a serum is. Even if you're the proud owner of several serums, it's not a particularly clear product on it's surface. Think of the contradictions: It's moisturizing, but you still use moisturizer. It can be oily, but it's not necessarily face oil. It can be watery, but is it essence? So many questions and we haven't even gotten to ingredient lists yet! Skincare should never stress you out (that would sort of defeat the purpose), so we pooled our collective knowledge, did a bit more research, and compiled a cheat sheet of sorts. There's not going to be a test, but study up anyway. We hear skincare talk makes great party ice breakers. What is serum? Serum is a skincare product you can apply to your skin after cleansing but before moisturizing with the intent of delivering powerful ingredients directly into the skin. Serum is particularly suited to this task because it is made up of smaller molecules that can penetrate deeply into the skin and deliver a very high concentration of active ingredients. This makes them a great tool for targeting specific skincare concerns, like wrinkles. Goodbye, signs of aging! Is serum a moisturizer? Yes and no. Serums can be chock-full of moisturizing ingredients (hyaluronic acid, ceramides) to help skin retain moisture. But, that doesn't make them moisturizers in the traditional sense. Face lotions and creams are richer and create a barrier on top of the skin to keep all that good stuff in. How often should I use my serum? Well, this all depends on the serum. Read the label, but once a day will probably cover your bases. What's the difference between serum and face oil? Good question. Traditional serums are water-based. Though, as the face oil trend grows (and there are more and more oils on the market), more oils are marketed as 'serums.' Office favoriteVintner's Daughter Active Botanical Serum comes to mind—it's very much a face oil. Use whichever floats your boat, with Aida Bicaj's soothing voice in your head, saying these words: "You have the water-based serums and the oil-based serums. Water-based serums go under the cream and they are so important. They nourish the inner layer of the skin because the molecule is very small so it penetrates—because of the P50, of course. The oil-based serums go on top of the moisturizer because they have a bigger molecule. They're supposed to keep the cream and whatever you put underneath moist during the entire day. There are so many products out there and everybody claims that it’s the best, so consumers are confused as to what works for them."