These terms are connected, and you also need to read about [Page Resources](/content-management/page-resources) and [Image Processing](/content-management/image-processing) to get the full picture.
The illustration shows three bundles. Note that the home page bundle cannot contain other content pages, although other files (images etc.) are allowed.
While Hugo supports content nested at any level, the top levels (i.e. `content/<DIRECTORIES>`) are special in Hugo and are considered the content type used to determine layouts etc. To read more about sections, including how to nest them, see [sections].
The following demonstrates the relationships between your content organization and the output URL structure for your Hugo website when it renders. These examples assume you are [using pretty URLs][pretty], which is the default behavior for Hugo. The examples also assume a key-value of `baseURL = "https://example.com"` in your [site's configuration file][config].
`_index.md` has a special role in Hugo. It allows you to add front matter and content to your [list templates][lists]. These templates include those for [section templates], [taxonomy templates], [taxonomy terms templates], and your [homepage template].
You can create one `_index.md` for your homepage and one in each of your content sections, taxonomies, and taxonomy terms. The following shows typical placement of an `_index.md` that would contain content and front matter for a `posts` section list page on a Hugo website:
The [sections] can be nested as deeply as you want. The important thing to understand is that to make the section tree fully navigational, at least the lower-most section must include a content file. (i.e. `_index.md`).
Single content files in each of your sections will be rendered as [single page templates][singles]. Here is an example of a single `post` within `posts`:
The following concepts provide more insight into the relationship between your project's organization and the default Hugo behavior when building output for the website.
A default content type is determined by the section in which a content item is stored. `section` is determined by the location within the project's `content` directory. `section`*cannot* be specified or overridden in front matter.
The `slug` is the last segment of the URL path, defined by the file name and optionally overridden by a `slug` value in front matter. See [URL Management](/content-management/urls/#slug) for details.
The `url` is the entire URL path, defined by the file path and optionally overridden by a `url` value in front matter. See [URL Management](/content-management/urls/#slug) for details.