If you have OCD like me you hate it when some apps are round, others are square, and some are bigger than others on your homescreen. As a result, our phones start to look messy at times. This is why iOS has every icon the same size and shape, so it's uniform and clean.
Well, Google added something called Adaptive icons to Android Oreo. Now, if a developer supports it, the operating system will automatically adjust it to match the shape and size of every icon you already have.
Google also said icons are dynamic and can move. Like the calendar icon on your phone always shows the correct date, and the same goes for the clock. However, we're not seeing that yet on the Pixel XL.