there are about 6 different species of zoa/paly fauna...
three main ones we recognize in this hobby are palythoa, protopaly, and zoanthid...
palythoa are those large button polyps like green implosions and brown paly's...
protopaly are they like nuclear greens, purple deaths, captain america's and those sorts...
zoanthids can be itself cut down to several sub species... zoanthids, being small zoas like tubs true blues, kind midas... zoanthagrandi or something like that are the people eater variety... like PPE RPE ding dangs... i'm forgetting the other sub species that is like pink zoas and such... i'll have to hit the books again...
there also zoanthidpalygrandi and amphipalythoa in the trade... like nightmares, pink quazars and green palygrandi... but those are the more rare polyps...
ninja edit: to make it less confusing, paly's use calcium in their bodies and make sand inside of them... some of them... but in this hobby there is so much politics on species and family it's hardly known... but i think us as enthusiast should read up more about the scientific factors and learn as much as possible of our animals...