A map, vista, or survey view can help people to understand their position relative to the whole and form an additional mental model of the landscape. In addition to helping with pure navigation, maps often make conceptual relationships between things clearer than they would be if people just navigated through them.
In the real world, universities, theme parks, shopping malls, and airports all often provide maps near entrances to show where a person is currently located relative to where they want to be. Many times, as in the case of subway systems, these maps are more useful when they are symbolic, rather than literal. The famous London tube map, for instance, ignores actual distances and the oddities of the landscape, and instead just makes the train lines, stops, and connections clear. Grocery stores have signs above each aisle indicating the goods present there. These goods are usually listed in columns that correspond to each side of the aisle, and appear in the rough order on the sign that they do in the aisle. Seeing these lists helps people find specific things, but also understand the other kinds of things that ought to be there. An aisle that has sugar, flour, and cooking oil probably also has other baking supplies.
In the digital world, literal maps are almost never useful, but symbolic ones are. E-commerce sites often provide a clear view of the site hierarchy through persistent navigation, which helps users see the whole site without clicking into different areas. Similarly, category pages arrange and give a preview into their contents below, helping users intuit how they’re organized and what’s likely to be there.