Just as you might suspect, a primary menu is the top-level menu used on a WordPress site.
In WordPress, menus are clickable options that are displayed on your website both on the front page as well as on each individual page or post. You can set up multiple menus or just one, and where these menus are displayed on the screen is determined by your theme.
Menus can be stacked and nested in a hierarchy so that clicking on one menu option opens up a new menu. Regardless of whether you have a “flat” or “hierarchical” menu, you must choose which menu will be displayed in the primary menu area.
To do this, log into your administration panel and click on “Appearance” in the left-hand side of your screen and then “Menus.” From here, you’ll be able to modify how each menu works and the structure of each menu as well as which menu will be used for the primary menu.
The easiest way to think of the primary menu is as a fixed piece of real estate on your website. For most WordPress sites, the primary menu is the menu displayed across the top of the front page and above all individual posts and pages. The menu editor allows you to change the name and content of each menu, including which menu will be displayed in the “primary menu” space on your website (as determined by your theme).
When you install WordPress, the default setting is for the primary menu to link to all of the existing pages on your website. You can customize which pages are shown for this menu or create a brand-new menu based on different criteria and then display that in the primary menu slot. The choice is up to you, but you must choose one menu to be the primary menu.