I really like the ability of google photos to generate new albums based for example on a trip I made. I don’t exactly know how it is generating those. My best guess is depending on the gps tags and if the gps data in a certain amount of photos across a certain range of days is vastly different than the “usual” gps data.
This would probably require a certain amount of machine learning to get right.
Plus google photos chooses only a few pictures from that time range - also probably based on some kind of “what is a good photo” algorithm.