A Microsoft file hosting and synchronization service.
OneDrive certainly can and does delete files and folders on your local PC all by itself, even though they are not supposed to be synced. This has happened to me twice today, and I am now sure it is OneDrive doing it and not my PC simply deleting stuff spontaneously. If I'm to be able to do any work without the danger of it being wiped out I will have to keep OneDrive permanently disconnected from my PC. Appalling.
I keep copying over my backed up files from an external hard drive onto my freshly cleaned up C:/, then the moment I link OneDrive it ignores my settings about which folders to sync (just one, which I don't have locally) and starts deleting my local folders (which are very large and very important to me...!) in a bid to replace them with older folders with the same name that it has online. To be clear: this has happened twice today, even though I twice made sure all options for OneDrive back-up were deselected (to no avail - I could see the round little arrows indicating that the folders were being uploaded to OneDrive), and even though before the two wipe outs I made sure I had selected only a single folder for syncing/making available offline, a folder which only exists on OneDrive. Basically OneDrive will ignore your settings and do what it wants to your PC, emptying your folders willy-nilly, and Microsoft will tell you that you are imagining it.
It's actually the second time that I have had a massive loss of data due to OneDrive going insane; this time I was better prepared than last time, when it wiped out all of my local files in not one but two laptops and replaced them with the (much older, much smaller) set of folders and files I had saved in it. I sought Microsoft's help at that time - that was 2017 I think - and they were absolutely useless. It appears the problem continues and Microsoft neither understands it nor is able to fix it.