When configuring classic SharePoint sites for navigation, you will typically spend a lot of effort designing and customizing themes. Some of the drawbacks of the classic SharePoint experience is the lack of responsive themes and the high degree of coding skill necessary to create custom master pages and alternate CSS configurations.

Classic SharePoint has two main navigation methods: structural navigation and managed navigation. Structural navigation is just that—it's based on the site structure of your tenant. Managed navigation is created using term sets to define a navigation structure and friendly URLs.

Creating a managed navigation structure requires four advanced configuration steps: enabling publishing features for the site, creating a term set to be used for navigation, adding terms to the term set, and then updating the navigation properties in the Site Settings | Look and Feel | Navigation Settings section of a site. 

The following process can be used to enable and configure managed navigation.