LPS are a type of coral, it stands for large polyp stony. SPS stands for small polyp stony. Then there are a third kind, called soft corals. As far as difficulty keeping goes, softies are easiest, followed by many LPS, and most SPS are more difficult to keep. Some common LPS corals are open brain, frogspawns and hammer corals, blastos, bubble corals, trumpet and candy cane corals, etc.