If I delete contents from iCloud drive does that I'm deleting contents from the MacBook Air?

Also, is there a way of transferring contents from iCloud drive to Mac and if so, how is it done? I want to delete everything in my iCloud and keep those contents on my Mac.

If you delete the contents of iCloud they will be lost so you will need to move the contents from iCloud drive to an external drive or a different folder on the Mac

Open Finder and go to the iCloud Drive folder.
Drag an item to a different folder on your Mac.

Your iCloud and MacBook are separate storage points.
the exception being if the only place you had it stored on your MacBook was your iCloud folder, which is synced with the server on changes.
if they are just in your Pictures or Documents folders or other folders, deleting them in iCloud will not change the MacBook ones.
honestly, this is why i dislike "cloud" as a backup option. Too confusing…