Preventing from Author/Tag/Categories pages to be created

Hello, general Wordpress question: i have noticed that Wordpress automatically creates pages for Author/Tags/Categories. How can I prevent these from being created?

Also as a separate question, I have a page that I do want to be on my website but I do not want it to show on google results. How do I prevent the page from appearing on Google while still staying live on my website?

Thanks a lot,

Ronan