A Microsoft file hosting and synchronization service.
If OneDrive was not enabled when you deleted the files, then it was not syncing at that time, so if you deleted files, the files were not deleted form OneDrive.
If OneDrive is now syncing your files, delete the files on your PC again and that will also delete the files from your OneDrive account online and they will not sync back down to your PC.
You can also log into OneDrive online in a web browser (https://onedrive.live.com/) to delete any files you do not want to sync back down to your PC.