Each time you create a new page, it will load a default template onto the editing box. The template aims to create a homogeneous and predictable layout across pages. Therefore, you should use the default template as far as practicable.
In order to improve presentation and page formatting, the default template may change over time. When this occurs, only new pages are affected. Older pages need to be updated manually. Thus, you may encounter different "standards" on site. Yet, you should use the default template that loads onto a new page as far as practicable. If you need pages as examples, you should refer to the most recently created pages, as these shall show the newest layout.