A question mark folder on a MacBook is a special folder that is created when a file or folder is moved to a location that it is not allowed to be in. For example, if you try to move a file from your Desktop to your Applications folder, macOS will create a question mark folder in the Applications folder and move the file there. This is because the Applications folder is a protected folder and only contains applications that have been installed through the Mac App Store or from a developer.
Question mark folders are also created when a file or folder is moved to a location that does not exist. For example, if you try to move a file to a folder that has been deleted, macOS will create a question mark folder in the parent folder and move the file there. This is because macOS does not know where to put the file since the folder it was supposed to go to no longer exists.
