Part of macOS

`cloudd`iCloud sync

○ Leave it

Syncs app data with iCloud.

What it is

Moves data between apps on your Mac and iCloud, such as notes, reminders and app settings.

Why it might be busy

After setting up a new Mac or changing lots of iCloud data. Usually until syncing finishes.

If you stop it

macOS starts it again straight away. Leave it.

○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.

From Procession’s guide, in the words the app shows.