This may be my Celiac Disease blog, but don’t take my word for what gluten is as I’m not sure I would even be able to explain it very well at this point, but I’m learning. These sources help:
What’s the big deal with gluten? – William D. Chey (TED Ed)
“Gluten is a general name for the proteins found in wheat (wheatberries, durum, emmer, semolina, spelt, farina, farro, graham, KAMUT® khorasan wheat and einkorn), rye, barley and triticale – a cross between wheat and rye. Gluten helps foods maintain their shape, acting as a glue that holds food together. Gluten can be found in many types of foods, even ones that would not be expected.” (source: celiac.org)
“Gluten is a storage protein found in wheat, barley and rye. Gluten can also be found in derivative of wheat, barley and rye gains such as malt and brewer’s yeast. Gluten gives dough its elasticity, acting like a glue, giving bread its classic chewy, soft texture. (source: beyondceliac.org)
Science: What is Gluten? Here’s How to See and Feel Gluten