Gluten

Gluten is a plant protein found primarily in wheat. In bread baking, gluten strands trap the carbon dioxide released by yeast in the process of fermentation, enabling bread to rise properly and maintain its light and lofty height.

High gluten flour is usually a 50/50 blend of vital wheat gluten and all purpose flour.

Bread flour is milled from hard wheat, which is very high in protein and gluten. Bread flour is used in many
recipes that are baked in the bread machine, as the loaves are higher rising and have a better texture.

I am not sure what you bought in the bulk food's. It may be the vital wheat gluten if it said 0 carbs as wheat flour would have some carbs in it. If it is the vital wheat gluten I like to mix 1 TBSP of it in with my flour when baking bread rather than using the High Gluten Flour or I use the bread flour.