About Rain Shower Heads
Rain shower heads are high-volume shower heads that are typically large in diameter and are ceiling mount configurations, but that is not always the case. The key is that they are high volume, but that's not always true. A high-efficiency faucet that feels like its high volume will qualify as a rain shower head.
About Ceiling-Mount Shower Heads
Most ceiling-mount shower heads are going to technically be rain shower heads, but that's not always the case.