Toxin antitoxin systems are ubiquitous across bacterial genomes and are central to the physiology of many prokaryotes. These systems can be broadly classified as type I, II, III, IV, and V based on the nature of their antitoxins and toxins. A major evolutionary driver of these systems is the broad range of potential toxins produced by bacteria and the need to protect against suicide or competition from related bacterial species. Synonyms for toxin antitoxin systems include TA systems, addiction modules, plasmid stabilization systems, programmed cell death systems, and bacterial immunity systems, reflecting the diverse functions and phenotypes attributed to these systems. Understanding the molecular mechanisms of these systems is essential for developing new antimicrobial therapies and understanding the regulatory principles that govern cellular function in bacterial communities.