This inner page template is versalite allowing you to add all manner of built-in Hubspot modules and also more custom modules which are included with the template. A Rich Text module is a great way to start off and introduces your content in as much detail as needed. Some lesser used but useful tools of the Rich Text editor include the 'Tools > Show blocks' which can help in preserving text formatting and 'Source code' for users who have HTML experience. Modules can be added in the 'Main Column' and 'Sidebar' sections of the page editor.
This template is useful for websites which have more than a few pages within the navigation. The navigation in the sidebar is dynamic and will show pages that are related to the section being viewed. The sidebar is also a useful place to add aditional content which supports the main column content, CTAs sit very well here.