You can delete whole pages by clicking on the delete button of the page in the page tree.
Depending on enabling/disabling the page trash at the website settings, the page will be quashed immediately or sent to a trashbin (that means, a page in the trashbin is not accessable from backend or frontend any longer, but still exists in the database and can be restored by clicking on the restore icon).
For final removing a page you have sent to the trashbin, you have to click on the delete button of the page again.
Please note!