icloud vs icloud drive

iCloud is the overall "name" for any iCloud service, like iCloud Drive.

You can't save files/content to "iCloud". You save to iCloud Photos, Drive etc.

If iCloud is thought of like a pair of pants, iCloud Drive is one of the pockets.

See >> https://support.apple.com/en-ca/guide/icloud/welcome/icloud

why there are pages, numbers and keynote both on the home page as well as 'icloud drive'?

Those are apps, not storage places.

Using the apps and saving documents will place those documents on iCloud Drive in folders named for the apps.