Annelids are a group of segmented worms that belong to the phylum Annelida. They are characterized by their long, cylindrical bodies divided into repeated segments, which can help with movement and flexibility. Common examples of annelids include earthworms and leeches. They can be found in various environments, including soil, freshwater, and marine habitats. Annelids have a complex body structure that includes a coelom, a fluid-filled body cavity that aids in movement and organ function. They possess a closed circulatory system, which means their blood is contained within vessels. Annelids play important roles in ecosystems, such as improving soil health and serving as food for other animals.