What invertebrate group does the eathworm belong in?

Earthworms belong to the phylum Annelida (ringworms). Note that these are not the only kind of worms; two other phyla are Platyhelminthes (flatworms) and Nematoda (roundworms), and they're all very different from each other. For comparison, another phylum-phylum difference is that between either of the worms and Chordata, being all vertebrates!