What is the purpose of location indicator and index indicator in GUI map configuration?

In cases where the obligatory and optional properties do not uniquely identify an object, WinRunner uses a selector to differentiate between them. Two types of selectors are available:
A location selector uses the spatial position of objects.
The location selector uses the spatial order of objects within the window, from the top left to the bottom right corners, to differentiate among objects with the same description.
An index selector uses a unique number to identify the object in a window.
The index selector uses numbers assigned at the time of creation of objects to identify the object in a window. Use this selector if the location of objects with the same description may change within a window.