The paper presents new data indicating the composition of the human gastrointestinal microbiome, consisting of bacteria, archaea, viruses (including bacteriophages), as well as eukaryotic and heterotrophic organisms such as fungi – the existence of which in the gastrointestinal tract is referred to as the mycobiome. The human digestive tract, divided into the oral cavity, pharynx, esophagus, stomach, and small and large intestine, inhabited by the microorganisms mentioned above, forms a specific qualitative and quantitative, rich and diverse specific ecosystem. Thanks to the use of bioinformatic and molecular methods, including metagenomic sequencing, it is still being discovered. In this review, systematic groups of bacteria, archaea, viruses, and fungi occurring in individual sections of the gastrointestinal tract are presented, and enterotypes of the large intestine are indicated. Considering the amounts of the above-mentioned groups of microorganisms in individual sections of the gastrointestinal tract of the human, the environment of the large intestine and oral cavity are the richest parts of the microbiome, while the throat and esophagus are the poorest. Among the microbiome of the digestive tract of the human, the most numerous group are bacteria located in the mouth and small intestine, while the the most limited group of bacteria is registered in the pharynx and esophagus. Archaea, on the other hand, have been described most frequently in the large intestine and stomach, and were not found in the throat and small intestine. Most viruses in the gastrointestinal tract were found in the large intestine and the oral cavity, while they were absent in the stomach. The fungi found in the microbiome were most abundant in the large intestine and stomach, and the smallest amount in the throat and small intestine.