Annelids are worms with segmented bodies (Latin, annellus = little ring).  The annelid body consists of a head, a segmented body that is a sub division of the body into a series of repeated units, and a terminal portion. Unlike nematodes annelids have a specialized digestive organs.

Earthworms, leeches, and tubeworms are the members of this phylum.  Earthworms live in land, leeches are fresh water and tube and sand worms, which are, know, as polychaetes are marine animals.

Earthworms are the largest group of annelids.  They feed on decayed organic matter in the soil and are very important ecologically.  

Leeches are carnivorous or parasitic (feed on tissue fluids, or blood).  They lack bristles (hair like structures that assist locomotion) that are characteristics of other annelids.  In the old days the blood-sucking leeches were used in medicine to clean up the wound, and today leeches are used to help patients to recover from plastic surgery.

The Polychaetes (tube worms) are important part of food chain in the marine environment.  Most polychaetes build tubes and live in them.  They have a pair of fleshy appendages on each body segment beside the bristles.