A locator map, sometimes referred to simply as a locator, is typically a simple map used in cartography to show the location of a particular geographic area within its larger and presumably more familiar context.

Whats the difference between a map and locator map?

The main distinction of a locator map is that it can track players, while a normal map cannot. A map's main function is to see the surface of any texture, unless you are in the Nether.

What locator means?

: one that locates something (such as a mining claim or the course of a road)