Small details most people never notice.
Movies have a LOT of layers. There are plenty of things going on in any given scene that most audience members will never explicitly notice, but that make a difference to the scene regardless.
It could be a decorative prop that subtly references something important about the character, or even a line that's spoken in passing that just adds that much more depth to the film if you really pause to think about it. Thankfully, there are some eagle-eyed observers
out there who help us catch the things we'd otherwise miss.