A Locator map is used to show the relative location of the place that is being focused on in the map in terms of the larger area where it is located.
The locator map is usually located in a smaller box on the map and in it the area that is being displayed prominently on the map is then shown in terms of where it is on the larger area that it is in.
For instance, if the main map was a map of the state of Colorado, the locator map might be in a box at a corner showing where Colorado is in the United States.
