The Default Template is applied automatically to your pages by “default”. It will show the “Content Sidebar” on the right but only if there are widgets in the sidebar. If there aren’t any widgets in the sidebar then the content will expand to fill the entire width.
I’m showing you this page without a feature image set because I have the built in feature slider activated. The slider or the grid will appear on the home page only. When you set a feature image it appears above the page title and is 674 pixels wide by 100% height of the image. If you do not set a feature image then the page title appears at the top and content underneath. You can insert media, like video or images into the content area and it will appear with the text.