*`posts/` has the blog posts but really they can live in any directory. They need only the `post` tag to be added to this collection.
* Add the `nav` tag to add a template to the top level site navigation. For example, this is in use on `index.njk` and `about/index.md`.
* Content can be any template format (blog posts needn’t be markdown, for example). Configure your supported templates in `.eleventy.js` -> `templateFormats`.
* Because `css` and `png` are listed in `templateFormats` but are not supported template types, any files with these extensions will be copied without modification to the output (while keeping the same directory structure).
*`_includes/postlist.njk` is a Nunjucks include and is a reusable component used to display a list of all the posts. `index.njk` has an example of how to use it.