iCloud & iCloud Photos · iCloud Drive basics
Why are there app folders like Pages and Numbers in my iCloud Drive?
Short answer: Apps that save to iCloud — Pages, Numbers, Keynote, TextEdit and others — get their own iCloud Drive folder so documents appear on all your devices. Deleting a folder deletes those documents everywhere.
Apps that store documents in iCloud get their own folder in iCloud Drive — Pages, Numbers, Keynote, TextEdit, Preview and many third-party apps. It's where those apps save documents by default so they appear on all your devices.
They're ordinary iCloud folders: their files count against your iCloud plan and can be made online-only like any others. Deleting the folder deletes those documents everywhere, so check what's inside first.
If one app's folder is large, open it in Finder, sort by size, and decide what to keep. Storage Studio's Duplicates window can also spot exact copies among the files already downloaded to your Mac.