Reference:
An application can have as many application menus as the application design requires. An application menu is a container for application modules, which are links to features or functionalities within an application. Application menus are displayed in the application navigator, which is the left sidebar of the ServiceNow interface. Developers can create and configure application menus using Studio or the Application Menus module. Application menus can have different roles and visibility settings, depending on the intended audience and purpose of the application. References: [ServiceNow Docs - Application menus], [ServiceNow Docs - Create an application menu]