A Microsoft file hosting and synchronization service.
OneDrive is not a backup, it’s a cloud location of your data.
The default installation of Office 365 and its OneDrive component uploads all the contents of the PC \My Documents\ folders to OneDrive, (syncs) and there will be a OneDrive folder in File Explorer containing cached copy of all the OneDrive content. And in Word etc the default Save location is set to OneDrive.
No Docs/data is stored on the local PC
You cannot remove OneDrive on a retail O365
On an Android the mobile has specific settings re OneDrive & pics