Indigenous: In this case, indigenous refers to the natural bacteria population of an individual’s intestines—the bacteria that would be present even if they never ate probiotics.

Fermentation: The chemical breakdown of substance to produce energy without consuming oxygen.

Pathogen: A bacteria, virus or microorganism (something realllly small) that can cause disease.

Prebiotics: The ingredients that are used as starting materials for fermentation by the resident bacteria in our guts.

Probiotics: Food or supplements containing living, good bacteria. This definition is pretty broad, and scientists still don’t know much about which bacterium are good to have in probiotics, but for now we’ll just say any food that has live bacteria that won’t cause disease is a probiotic.