{{Sidebar/doc}} is a template that lets you create sidebars, as defined at sidebars. Please do not overuse this template. Sidebars are only very rarely needed. The narrative situation must be extremely convoluted and confusing in order to justify the use of a sidebar.
Usage
{{sidebar|title=Whatever|Hello there. This is an example sidebar. See how it fits into the overall page design, but is automatically in a different font, so that you know it's not quite written from the same perspective?}}will produce: