A navigation is used to enhance the usability of a website and to ensure that users can navigate from page-to-page via a clearly defined menu structure. A navigation is used to provide links to users and to help them understand what other pages are on the website, if a link is clicked, the user will navigate to another page.
A lot of web designers tend to place their navigation at the top of the page that’s above the fold, to ensure that users can clearly see the menu on the first visit from a desktop device. On a mobile device, the navigation may be hidden unless clicked by an icon.
Not only is it important for the users to be able to understand the navigational structure, it’s also critical that search engine spiders can also understand and interpret the navigation also, otherwise, they won’t be able to navigate from page to page. This will result in other pages on your site not being indexed, as search engine spiders navigate from page to page using the website links.