how do people learn all of the names of corals just by looking at them? I’ve been trying for awhile now and have yet to be able to retain all of the names
First off, many of the names refer to the genus and aren't species specific which makes it a LOT easier. Usually looking at the polyp structure and how they're connected as well as the growth form can give pretty good clues.
I know if the coral is (SPS,LPS,soft). Let’s say I’m looking at an LPS for example. I have the Information to know if it’s an Acan, chalice, torch. Just by looking at them. But I don’t know the name it’s sold by. I’d recommend going into a LFS and getting familiar with the names. Hope this helps!
I can recommend some good books...you'll frequently encounter the same corals over and over which makes it easy after a while to automatically recognize characteristics.
There are unique features of different genera however, such as the presence of an axial polyp on Acros. (The tip of each beach will have a polyp at the end.)