Click on the skinny orange button if necessary to expand the left column;
Click on the tool icon for Page Details (a white "i" in a blue circle) in the orange block at the bottom-left.
You will see a variety of information about the current page, and will have the opportunity to change some of it. In particular, this dialog permits you:
to withdraw a page from public view entirely (to "deactivate" it);
to examine the templates from which this page is derived; see also the discussion of walking the template hierarchy.