The millions of skincare products out there is overwhelming, to say the least. If you really wanted a 20-step routine, you could have it. But would it be necessary? Of course not. However, there is something that should be non-negotiable for every skincare routine: Keeping skin moisturized.

For some, it’s as simple as applying a daily face cream, but in order to prevent and block lingering dehydration, irritation, or texture issues, you should become familiar with the three main categories of moisturizing and hydrating ingredients: humectants, emollients, and occlusives. If you have no idea what we’re talking about, no stress—below is your ultimate guide.

Although the three types of ingredients are similar in terms of benefits, they absolutely don’t function the same way. To begin with, humectants are ingredients that act similar to a sponge, in that they bind to water to pull it into the outer skin layer. Emollients work to help soften rough cells on the surface of the skin, as well as prevent water loss. And lastly, occlusives form a protective seal over the outer skin layer, preventing loss of hydration to the environment.

It’s important to brush up on when you should be using products that contain these ingredients. Below, get the lo-down on everything you need to know about each.

What are humectants?

Humectant ingredients keep the skin hydrated by absorbing water so that it stays locked into the skin. Some popular humectants include hyaluronic acid, aloe vera, lactic acid, and glycerin—found in many serums and moisturizers. To find out if you need to incorporate a humectant into your routine, pinch your skin and if the skin comes up and takes a while to go back down, your skin is dehydrated and could benefit from a humectant.

Skin that lacks water and hasn’t completely dehydrated (cracked) would benefit from humectants. Daily use also prevents dryness and helps to maintain the skin’s moisture level. When you put on a humectant, make sure you also follow up with a moisturizer on top to further prevent water loss.

What are emollients?

Similar to humectants, emollients are all about adding moisture to the skin by preventing water loss. And truthfully, they work best on top of a humectant to lock in water. Think of them like a layer or blanket that will hold all your skincare products in place. Their main goal is to repair cracks in the skin’s barrier and soften the skin. And luckily, they can be used on all skin types. And, like humectants, you will want to use emollients regularly to prevent dehydration.

The most common emollient? Ceramide, or the lipid that make up the skin barrier. They help keep skin looking smooth, dewy, and moisturized. Argan oil and Vitamin E are two other popular emollients to look at for at your local drugstore. If you have oily skin, it would be a good idea to find moisturizers and body lotions filled with emollients as it will stop the skin from becoming scaly or wrinkly.

What are occlusives?

Occlusives, like the other two categories above, help prevent water loss. The main difference, they are for the more extreme cases of dryness and dehydration. Out of the three, occlusives are the heaviest and most moisturizing because they work to form a protective layer and create a barrier on the skin’s service.

Common occlusives include petroleum, petrolatum, and dimethicone, as well as most waxes, oils, and types of butter. However, this category isn’t necessarily good for oily or acne-prone skin because they’re generally comedogenic (read: they’ll clog your pores). But if you have a skin condition like eczema or psoriasis, you might want to grab an occlusive.

If you find yourself dehydrated, here’s some tips on how to drink more water.