The human microbiome is made up of the genomes of the microbiota that live on and within us, such as protozoa, archaea, eukaryotes, viruses, and predominantly bacteria. The microorganisms that thrive in the digestive systems of humans and other animals, including insects, are known as gut microbiota, gut flora, or microbiome. The gastrointestinal metagenome is the collection of all gut microbial genomes. Human microbiota is primarily located in the gut. It is estimated that the gut flora has a hundred times the number of genes found in the human genome. The composition of the human gut microbiota is connected to health and disease, but understanding the biological roles of different bacteria species is required.