A gluten-free diet is one that excludes the protein gluten. For those suffering from celiac disease, gluten causes inflammation in the small intestine and can make it difficult for them to digest food and absorb important nutrients.
Additionally, for those suffering from non-celiac gluten sensitivities, avoiding gluten can prevent symptoms such as abdominal pain, fatigue, headaches, etc. Learn more about gluten-free diets and what those suffering from sensitivities should avoid here.
For more information on celiac disease, check out this great blog post from Jen Reviews.