Guar (gwar) gum is used in gluten-free cooking to bind, thicken and emulsify gluten-free ingredients. If you don't add it to most of your gluten-free baked goods, they will likely end up as a pile of crumbs!
Guar gum comes from the seed of bean-like (legume) plant, sometimes referred to as the Indian tree. It is high in soluble fibre. Guar Gum has eight times the thickening power as cornstarch. Like xanthan gum, measure carefully when using guar gum in gluten-free recipes or you may end up with heavy, stringy baked goods.