It is a well-known idea that humans have a large set of bacteria housed inside them, but it was not until the year 2001 that Joshua Lederberg would officially coin the term ‘microbiome’ in reference to the ecological community of commensal, symbiotic and pathogenic microorganisms that share our body space. Since that time, the advancement of technology has allowed for much more efficient sequencing and studying of the exact microbiota dwelling symbiotically within humans. The oral cavity houses the second highest amount of microbiota in the human body, 700 species, only behind the gut which boasts over 1,000 different bacterial species. This review article explores the large database of research that supports the complex relationship humans have with the bacteria inside them. Many different factors contribute to the formation of a person’s oral microbiome including a person’s lifestyle and diet choices, as well as societal factors such as antimicrobial and pesticide use. Research has suggested that the relationship between microbiome and host is constantly changing to meet the ever-changing conditions pertaining to human life. While some bacterial species can be assistive in helping humans develop adaptive immunity and biofilms, other species can contribute to health complications such as gingivitis, dental caries, and even neurodegenerative diseases. While a lot of research is still needed to establish exact mechanisms on how these bacteria acquire entry into other parts of the body and the central nervous system, it is clear that their impact expands farther than just their oral cavity home. Bacteria in conjunction with human life cannot be seen as all-assistive or all-destroying. Depending on the bacteria present and its location within the body, its effects can be extremely life-sustaining or extremely life-threatening.