Small Polyped Stony (SPS) hard-corals have small polyps. Examples: Acropora.
These corals are generally considered moderate to difficult to keep.
Large Polyp Stony (LPS) corals are generally larger calcareous corals with large fleshy polyps. Hard-coral polyps form hard, calcium carbonate skeletons for protection and have six-fold symmetry. Small polyp corals are only a few millimeters wide, while large polyp corals can be over a few centimeters. Examples: Bubble and Hammer.
Soft Corals are held together by a jelly-like mesoglea and rigid, spiny structures called sclerites and have eight-fold symmetry. Soft corals produce a broad range of chemicals to avoid predators. Examples: Sinularia.
Colony Polyps contain symbiotic algae. Examples: Zoanthid, Sympodium.
Mushroom Corals. Examples: Rhodactis, Actinodiscus, Ricordea yuma.
Generally considered easy to keep corals.
Candy Cane (Caulastrea), LPS, Trumpet, Torch, Candy, or Bullseye
Favia (Favia), Favites, Moon Brain Coral, Pineapple Coral, Closed Brain Coral, Star Coral, Worm Coral, Honeycomb Coral
Frogspawn (Euphyllia paradivisa), Octopus Coral, Grape Coral, Honey Coral
Plate Coral (Fungia)
Lobo (Lobophyllia hemprichii), Lobed Brain Coral, Flat Brain Coral, Open Brain Coral, Meat Coral, Modern Coral, Large Flower Coral
Paly (Protopalythoa), Sea Mat, Button Polyps
Platy (Platygyra), Brain/Maze, Worm Coral, Closed Brain
Star Polyps (Briareum), Green Star Polyps (Pachyclavularia), Glove, Green Glove Polyps (Clavularia)
Torch (Euphyllia), Branching Torch, Trumpet Coral, Pom Pom Coral
Trachy, Wellso, Pacific Rose Coral, Open Brain Coral
Zoanthid, Zoas, Zoo
Generally considered moderately difficult to keep.
Some pictures courtesy of Unique Corals