OneDrive
Microsoft's cloud file storage. Launched in 2007 as Windows Live Folders, later SkyDrive, renamed OneDrive in 2014 after British broadcaster BSkyB won a trademark dispute over "Sky".
Deeply wired into Windows: File Explorer shows cloud files as ordinary folders and Files On-Demand downloads the contents only when you open the file, so a terabyte can "exist" on a 256 GB disk. 5 GB free, the rest via Microsoft 365 where the storage is effectively an appendage to the Office subscription. The business variant is called OneDrive for Business and is really SharePoint underneath, which explains its odd path-length and character restrictions. Automatic backup of Desktop and Documents is on by default, to many users' surprise.