Cloudinary is a cloud storage solution dedicated to storing and retrieving images. The primary feature is the ability to give you any resize or crop from your originally stored images (pretty important if you want to target web users with different sizes/crops/ aspect ratios / formats). Those transformations are then cached onto a CDN for fast retrieval. This would be pretty complex to roll out on your own on general purpose S3 storage. In addition, you get all kinds of effects that can be added onto images. You also get things like automatic face detection.