A section is a top-level content directory, or any content directory with an _index.md file. A content directory with an _index.md file is also known as a [branch bundle](/getting-started/glossary/#branch-bundle). Section templates receive one or more page [collections](/getting-started/glossary/#collection) in [context](/getting-started/glossary/#context).
The example above has two top-level sections: articles and products. None of the directories under articles are sections, while all of the directories under products are sections. A section within a section is a known as a nested section or subsection.
With the file structure from the [example above](#overview):
1. The list page for the articles section includes all articles, regardless of directory structure; none of the subdirectories are sections.
1. The articles/2022 and articles/2023 directories do not have list pages; they are not sections.
1. The list page for the products section, by default, includes product-1 and product-2, but not their descendant pages. To include descendant pages, use the `.RegularPagesRecursive` collection instead of the `.Pages` collection in the list template. See [details](/variables/page/#page-collections).
1. All directories in the products section have list pages; each directory is a section.
## Template selection
Hugo has a defined [lookup order] to determine which template to use when rendering a page. The [lookup rules] consider the top-level section name; subsection names are not considered when selecting a template.
A section has one or more ancestors (including the home page), and zero or more descendants. With the file structure from the [example above](#overview):
```text
content/products/product-1/benefits/benefit-1.md
```
The content file (benefit-1.md) has four ancestors: benefits, product-1, products, and the home page. This logical relationship allows us to use the `.Parent` and `.Ancestors` methods to traverse the site structure.
For example, use the `.Ancestors` method to render breadcrumb navigation.