What to include or save in iCloud?

See the article https://support.apple.com/en-in/guide/mac-help/mh36834/mac

When inbuilt applications box are turned on the data saved in them sync with iCloud Turn iCloud features on or off - Apple Support

Do you want to know what you should include in iCloud?

Or what an iCloud backup includes?

Please clarify what you want to know exactly.