Ajax Indicators - Confused

Interesting conversation about ajax indicator:

Jodie (my friend): what this means?
Alex (me): AJAX indicator.
Jodie what is an AJAX indicator?
Alex: Telling you your browser is busy... (Actually, I should say some AJAX event is happening).

After a while, Jodie showed me this page (http://www.napyfab.com/ajax-indicators/), said her computer is murdered...
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However, what an AJAX indicator means to you? Telling you some AJAX events happening behind the screen? Or... telling you some AJAX stuff is about to happen? Or just for developer's sake?