Hemichordata is a phylum of marine animals that includes acorn worms and pterobranchs. They are characterized by a body divided into three main parts: the proboscis, collar, and trunk. Hemichordates have a simple body structure and exhibit features that are similar to both chordates and echinoderms. These organisms play a vital role in marine ecosystems, often found in shallow waters. Hemichordates are primarily deposit feeders, consuming organic material from the sediment. Their unique characteristics and evolutionary significance make them an important group for studying the origins of more complex animals.