A postbiotic is an umbrella term for a preparation containing inactivated microorganisms and/or their components that is supported by evidence for a specific health benefit. Two practical requirements matter: (1) the preparation should be well characterized (which organism, how it was inactivated, which components are present, and at what dose), and (2) it should be linked to a measurable benefit in human studies. Postbiotics may influence gut barrier function, mucosal immune signaling, and inflammatory pathways, but effects are not universally interchangeable across products or people. That means selection should match the intended goal (e.g., gut comfort, susceptibility to infections, post-antibiotic recovery) and the individual’s risk profile. For children, pregnancy, and people with chronic disease or multiple medications, clarity on dose and intended use is crucial to avoid unrealistic expectations and to ensure the product chosen is appropriate and evidence-aligned.