This document summarizes characteristics of gram-positive cocci bacteria including Staphylococcus and Streptococcus species. It describes their morphology, habitats, pathogenicity factors like toxins and cell surface proteins, mechanisms of infection and spread, growth characteristics, and methods of diagnosis. Many are commensals of skin and mucous membranes but can become opportunistic pathogens, especially S. aureus and S. intermedius. They produce various exoenzymes and toxins like hemolysins and superantigens that damage tissues and avoid immune responses, allowing infection of sterile sites.