This is your own personnel Cloud Server. Store your movies, pictures and all important documents. It has 2 or more Hard Drives that duplicates your data so that you never loose your all your important documents. When your SmartPhone picture gets full and you don't want to pay for I Storage you can upload from your phone into your Synology Server, thru an app on your phone. You can access your data from anywhere when your not at home. example: If you are away from home and want to share a video of your cat , use DS Files on your phone to access movie.
As for Hard Drives, I would recommend the Iron Wolf Drives. They are made for the Synology (NAS).