one drive is a product from Microsoft and in that you can store your photos and videos also you can store files. All your files are synchronized with pc, I phone or android phone.
You must have a Microsoft account i.e hot mail account. You access your file anywhere you go.
Microsoft is giving 15 GB of free space on cloud storage. They also give 1TB storage for Rs. 150 per month. If you have business an need file anywhere you go for eg. In office, at home and on mobile. You can access same file on mobile at home and in office.
If your mobile phone SD card becomes crash. Then all your saved data, photos, and videos will not be recover. If you have songs or videos of films which are downloaded then even if your SD card has crashed you can again download. But, if if have saved all your personal data, photos which you have clicked on mobile then you have lost it for ever. If you store all your photos and videos to one drive then you can again download it from your account.
Same is with computers, if your hard disk fails to detect or it is fully crashed then you cannot have your personal data or photos which you have saved in your computer. In this case, Also you can use one drive to store your data and whenever needed we can download it again.
My view is, You must backup your data on cloud storage, as your data may not be recovered. There are various companies which provide cloud storage such as dropbox google drive. Choose any storage but must backup your data.