The navigation feature is optional, however it comes quite handy for themes that support it. Usually the theme will create a top menu bar from it or left/ right side navigation pane. The configuration for the navigation feature in cfg.yaml basically provides a link list for every language of your website. Since the order of the links are important the shape of the configuration is a YAML list. For every link the URL and the link text need to be provided. See the example below.
navigation:
en_US:
- link:
text: Pankyll
url: en_US/Pankyll
- link:
text: Pankyll Themes
url: en_US/Pankyll-Themes
- link:
text: Pankyll Theme Example
url: en_US/Example-Sites
- link:
text: Categories
url: en_US/Categories
- link:
text: Tags
url: en_US/Tags