Butterflies are an additional activity available in Hogwarts Legacy, through which you can get access to 15 chests containing conjuration items. First you need to find a group of butterflies flying in the air and get close to them. They are not very well visible, but when you get close enough you should notice their icon on the mini map.
When you get close to them, they will start to move. Follow them and after a while they will lead you to a place where there is a chest linked to them. The current position of the butterflies will be marked on the minimap all the time, which makes it much easier to locate them again in case you lose them. Without finding the butterflies, the matching chest will not be available.
