Brachiopoda is a phylum of invertebrate animals called brachiopods. This phylum is often grouped with two other phyla (Ectoprocta and Phoronida) under the name Lophophorates.
The general characteristics of brachiopoids include: a pair of protective shells (giving them a superficial resemblance to the bivalves such as clams), a stalk protruding from the rear called a pedicle which anchors the animal to the sea floor, and a lophophore (a ridge with many tiny tentacles on it, which the organism uses to catch food particles floating by).
Brachiopod shells come in many different shapes and sizes. Brachiopods were extremely abundant during the Paleozoic era (both in terms of numbers of individuals and numbers of species), but were practically wiped out around 300 million years ago during the Permian mass extinction. Only a few species remain alive today.
From the science dictionary at http://biotech.icmb.utexas.edu/