Bryozoa are aquatic colonial animals, which are abundant in modern marine environments, and have been important components of the fossil record. In some places, the skeletal remains are so abundant that the fossils become an important rock-forming material. If you need a common name, then you can call them 'sea mats', 'moss animals' or 'lace corals' for some forms. The majority are marine, although brackish-water and freshwater forms are moderately common.

The word 'colonial' needs more explanation. It is applied to types of animals which reproduce (among other ways) by budding new parts asexually from the original animal. These new additions contain functioning individuals, capable of feeding independently, yet remaining attached to the rest of the the animal. Colonial animals include corals and hydroids, ascidians, graptolites and pterobranchs as well as bryozoans. Additionally, there is debate about coloniality in sponges. Bryozoan colonies have a superficial similarity with corals, but the anatomy of the bryozoan animal is much more complex.

The entire complex is called a 'colony'; the individual functional units can be called 'zooids', although 'polyp' is used for coral individuals, and 'theca' in the case of graptolites.

The Recent and Fossil Bryozoa website, developed and maintained by Philip Bock, contains:

• a listing of Bryozoa classes and orders
• a systematic listing of Bryozoa families
• an alphabetic listing of Bryozoa families
• an alphabetic index of Bryozoa genera
• an index to illustrated Bryozoa species and genera
• a list of colour photographs

Furthermore, the website provides links to other websites on Bryozoa, a link to the International Bryozoology Association (IBA) website, links to IBA conferences, a glossary for the Bryozoa, a list with links to relevant journals, etc. The Recent and Fossil Bryozoa Database provides taxonomic information to the World Register of Marine Species (WoRMS).