Background and Aim: FOOD is the fundamental need of human life and has nutrients that support growth and health. Gastrointestinal tract microbiota includes beneficial microorganisms which have therapeutic effects and are known as probiotics. The studies on appropriate probiotic strains have led to the separation and identification of specific metabolic byproducts of probiotics known as postbiotics. Materials and Methods In this review study, relevant data were collected by searching for the keywords of "probiotics, postbiotics, immune system, bioactivity, disease, health improvement, FOOD and pharmaceutical industries" in the Web of Science, PubMed, Medline and Scopus databases. All articles related to experimental studies were included in the study and articles without full text were excluded. Results: The probiotics must maintain their survival against inappropriate growth conditions of the processing, storage, distribution, preparation, and digestive system so that they can exert their beneficial effects on health. Conversely, probiotic metabolites can successfully overcome these unfavorable conditions and maybe a good alternative to probiotics. Considering their specific chemical structure, safety, long shelf-life, and the fact that they contain various signaling molecules, postbiotics may have anti-inflammatory, immunomodulatory, antihypertensive, inhibitory effect on abnormal cell proliferation, and antioxidant activities. Conclusions: Postbiotics can mimic the fundamental and clinical role of probiotics, and due to their unique characteristics, they can be used in a deLIVEry system (pharmaceutical/functional FOODs) to achieve health-promotion objectives and also prevention, and treatment of diseases.