This is your site's blog page, where an index of your most recent blog articles will appear. To post a new blog article, navigate back to the list of pages, select the "/post" page type using the dropdown menu above the page list, and click Add Page.

If you don't want to have a blog on your site, you can simply delete this page. You will also have to visit the Menus screen and delete it from the primary and footer navigation menus.

Oh, and in case you're wondering about the element below, it's a List. You can add one to a page wherever you want a list of other pages to appear. This particular List is configured so that it only shows blog articles.