Celebrities avoid it. Publishers try to sell books about living without it. And the National Foundation for Celiac Awareness says that as many as 18 million Americans have non-celiac gluten sensitivity.

Yes, everyone seems to dislike gluten—or at least feel better when they avoid it. But how many people actually know what it is?

Here, quickly and concisely, is a look at what you need to know about gluten:

What gluten is
Gluten is protein, plain and simple. It’s in wheat, barley and rye but also exists in other products, including salad dressings, seasoning mixes, vitamins and some beauty products. Because it’s so ubiquitous, eliminating it entirely from your life can be a challenge.

Where gluten isn’t
Gluten Pros & ConsGluten exists in grains, but it doesn’t exist in every grain. Rice, corn, quinoa, amaranth, buckwheat, teff and even oats are among the grains that are naturally free of gluten. That’s good news for people who want to avoid gluten but still enjoy foods made from grain.

Gluten-free doesn’t always mean healthy
One of the biggest myths about gluten-free products is that they are not processed. Fact is, the popularity of gluten-free products has spawned a whole lot of gluten- free foods that are, in fact, highly processed. The best way to avoid them is to read the labels carefully and look for only natural ingredients.

Gluten intolerance is real
People with Celiac disease must avoid gluten. If they don’t, they’ll experience severe belly pain and bloating. But they’re not the only people who can benefit from gluten-free diets. As you read above, there are 18 million Americans who have gluten intolerance or sensitivity. While there’s currently no test for intolerance or sensitivity to gluten, one way to find out if you’ll feel better going gluten-free is to give it a try for a week.

Gluten-free doesn’t have to mean going without
Many people who cut gluten from their diets simply go without it. No snacks. No junk food and no grains. But if you look hard enough, you can find a whole lot of health (and delicious) gluten-free snacks.