A Microsoft file hosting and synchronization service.
I just encountered the same problem, but in a worse way:
I am involved in astrophotography, so I have folders with hundreds of images of the same subject taken sequentially at night and also many calibration images (which at a glance look just black or gray). Hundreds of images that, after calibration and processing, become one astronomical image.
I have started backing up even my precious original folder on OneDrive, but this way the Photo Gallery becomes useless, until I can choose the folders that feed the Photo Gallery.
All the photos on my phone are mixed with hundreds of images not to look at, but to work with.
I think I will have to switch to some other oncloud storage.
Mauro.