Facebook trained Fashion++ by showing the AI thousands of images of outfits that were deemed "fashionable." What's innovative about the AI is that it offers suggestions that are subtle. It won't, for example, recommend that you go out of your way to buy an entirely new outfit. Instead, it will suggest swapping one or two items. It may offer even more subtle suggestions such as recommending that you tuck in your shirt or roll up your sleeves. It's also taking on a task that is often considered creative and subjective. The company imagines the AI one day helping fashion designers to create new looks.
As far as weird AI experiments go, Facebook has been on something of a tear recently. Last month, the company published a paper on how it's using Minecraft to train a digital personal assistant that can help with generalist tasks. The way we see it, weird AI is a lot more fun than murderous AI.