Streptococci are a group of spherical bacteria that often appear in chains or pairs. They are classified as gram-positive bacteria and can be found in various environments, including the human body. Some species are harmless and part of the normal flora, while others can cause infections such as strep throat, pneumonia, and skin infections. These bacteria are categorized into different groups based on their characteristics and the diseases they cause. The most well-known group is Group A Streptococcus, which is responsible for illnesses like pharyngitis and scarlet fever. Proper hygiene and medical treatment can help manage infections caused by streptococci.