Streptococci are a type of bacteria that are spherical in shape and often appear in chains or pairs. They are classified as gram-positive bacteria, meaning they retain a purple color when subjected to a specific staining process. These bacteria can be found in various environments, including the human body, where they can be part of the normal flora. Some species of streptococci are harmless, while others can cause infections. For example, Streptococcus pyogenes is known to cause strep throat, skin infections, and other illnesses. Proper hygiene and medical treatment can help manage infections caused by harmful strains of these bacteria.