Objective: This review aims to comprehensively evaluate the current evidence on the role of prebiotics, probiotics, synbiotics, and postbiotics—collectively referred to as “biotics”—in modulating the human gut microbiota and enhancing intestinal epithelial integrity. Findings: Biotics exert their beneficial effects through several mechanisms, including by promoting the growth of beneficial microbes, producing short-chain fatty acids (SCFAs), strengthening the gut barrier, and regulating immune responses. Prebiotics selectively stimulate beneficial bacteria, probiotics introduce live microorganisms with therapeutic functions, synbiotics combine the strengths of both, and postbiotics offer non-viable microbial components and metabolites that mimic probiotic benefits with enhanced safety profiles. Each type of biotic demonstrates unique and complementary effects across a range of conditions, such as inflammatory bowel disease, irritable bowel syndrome, obesity, constipation, and antibioti