Gut microbiota refers to the complex community of microorganisms — bacteria, viruses, archaea and fungi — that inhabit the human digestive tract. These tiny organisms collectively influence digestion, immunity, metabolism, and even mood. Scientists estimate that trillions of microbes live in and on the human body, with the majority concentrated in the gut. Although each person harbors several hundred bacterial species, the total diversity and balance of these microbes are key determinants of health. The gut microbiome (the genomes of these microorganisms) encodes many more genes than the human genome and contributes functions humans cannot perform alone: synthesizing certain vitamins, fermenting otherwise indigestible fibers to produce short-chain fatty acids (SCFAs) like acetate, propionate and butyrate, and training the immune system. SCFAs support colonocyte energy needs, maintain gut barrier integrity, and have anti-inflammatory effects; these activities link the microbiota to metabolic and immune homeostasis. Because the gut microbiota affects multiple systems, changes in its composition — often called dysbiosis — are associated with conditions ranging from inflammatory bowel disease and allergies to metabolic disorders and mood disturbances. Understanding these relationships is an active area of research and supports the rationale for monitoring and supporting a diverse, balanced microbial community. Factors that shape the gut microbiota begin at birth and continue across the lifespan. Mode of delivery (vaginal versus cesarean), breastfeeding, early antibiotic exposure, geography and environment (urban versus rural), contact with pets, diet diversity, and physical activity all influence which microbes colonize and persist. Diet is one of the most modifiable influences: fiber-rich foods and varied plant-based substrates promote fermentation by beneficial bacteria, supporting SCFA production. Environmental exposures and an active lifestyle also contribute to microbial diversity and resilience. For those seeking a clearer picture of their intestinal ecosystem, microbiome testing can offer compositional and functional insights. Stool-based analyses, including 16S rRNA sequencing and whole-metagenome approaches, reveal which microbes are present and what metabolic capabilities they carry. Interpreting results in the context of symptoms, medical history and lifestyle is important: a single test is a snapshot, not a diagnosis. Practical, evidence-based adjustments to diet and habits often follow from testing and clinical guidance. To learn more about foundational concepts and practical implications, see this overview on what gut microbiota is and why it matters: [what is gut microbiota and why it matters](https://www.innerbuddies.com/blogs/gut-health/what-is-gut-microbiota-and-why-does-it-matter). For reference or alternate hosting, the article is also available via GitHub Pages: GitHub Pages: What is Gut Microbiota and GitHub Mirror. For information on testing options, see microbiome test. In summary, gut microbiota comprise a dynamic, essential partner in human health. Preserving microbial diversity through diet, prudent antibiotic use, and healthy lifestyle choices supports many physiological processes that depend on a balanced gut ecosystem.