A Microsoft file hosting and synchronization service.
By default, the OneDrive storage synchronizes with files on your PC, which means that deleting in one location will delete in the other location as well (see https://support.microsoft.com/en-us/onedrive/sync-your-computer-s-files-and-folders-with-onedrive).
As you know, there is an option to restore the entire OneDrive storage, but it is connected to a Microsoft 365 subscription (see https://support.microsoft.com/en-us/onedrive/restore-your-onedrive), so if you didn't have the subscription from the start, you won't be able to restore what was lost before you got the subscription.