I use both OneDrive and Google Drive and I find them both good cloud storage options and I have my files backed up on both One Drive and Google Drive.
I mostly prefer Google Drive as it seems to be easier to use than OneDrive but both Google Drive and One Drive are good drives to store files and data in the cloud.
When you upload files to One Drive only yourself or anyone else that you permit to see the files will be able to see the files.
One Drive is a cloud storage option where you can remotely store and save your files to have as a backup and the files are private and only accessible by yourself or anyone else that you give permission too.
If nobody else has permission to view your files on One Drive then they cannot see or access those files.
I use One Drive myself to backup files and photos from my computer so that I always have them available in the even a hard drive crashes or something else happens.
It's always good to have your photos and other important photos and documents backed up into the cloud and on other storage devices.