On this screen you indicate the selected entity to which rights are given from the role. These rights are:
Navigating means that any menu item to the entity's overview screen becomes visible. In fact, this is the door to the entity. If you do not want users to be able to add certain entities. mutate or delete, in many cases disabling the navigation checkbox for this entity will suffice.
Override ("override") any permissions on fields or entities. If you want to refine the permissions on the entity using the two other authorization methods, uncheck the permissions you want to refine in the type authorization screen.