Leeches are segmented worms belonging to the class Hirudinea. They are primarily found in freshwater environments, although some species inhabit marine and terrestrial ecosystems. Leeches are known for their ability to attach to hosts and feed on blood, making them famous in both ecological and medical contexts. In addition to their role as bloodsuckers, leeches have been used in traditional medicine for centuries. They secrete anticoagulants that prevent blood clotting, which has led to their use in modern medical practices, particularly in reconstructive surgery and blood circulation therapies. Their unique biology and ecological roles make them fascinating creatures in the animal kingdom.