A Microsoft file hosting and synchronization service.
I have had the exact same thing happen. Although when I had my new computer built and Windows 11 installed, I told them I did not want the "365" subscription, just have Word and Excel added. I very pointedly told them I wanted nothing to do with any type of subscription. I don't know if they knew about OneDrive or not.
Last January, because each time I wanted to delete one photo or just one document from a file, the entire file would be deleted. I researched and found out OneDrive was causing this, so I uninstalled it.
Just two days ago I went to work with some photos and all my photos, documents, etc. had been hijacked by OneDrive. I searched for hours for a fix. Many places indicated a link needed to be undone from OneDrive. None of the fixes have worked.
Luckily I have most things on flash drives. But still OneDrive hijacked everything so thoroughly that my system will not even let me create a new file and wirk from the C drive. There was no information given to me about this from my PC guy or an email from Microsoft or OneDrive at all.
I'm totally in on suing Microsoft to make this hidden rip off fixed.