1. What is Gluten?

Gluten (from Latin gluten “glue”) is a protein composite that appears in foods processed from wheat and related species, including barley and rye. It gives elasticity to dough, helping it to rise and to keep its shape, and often giving the final product a chewy texture. Between 0.5 and 1.0 percent of people in the United States are sensitive to gluten due to celiac disease. Note that wheat allergy and celiac disease are different disorders.
source: http://en.wikipedia.org/wiki/Gluten