I am new to javascript and ran across this function definition on a web page. What is the purpose of the _HBEvent callback? I am not really interested in the code as much as the function _hbEvent definition. What event will cause it to be called???

var _hbEC=0, _hbE=new Array; function _hbEvent(a,b){b=_hbE[_hbEC++]=new Object();
b._N=a;b._C=0;return b;}
var hbx=_hbEvent("pv");hbx.vpc="HBX0200u";hbx.gn="www35.vzw.com";
hbx.acct="DM5701180EEZ;DM570203L6VD";
hbx.mlc="/messaging/text+messaging";
hbx.pn="Send+a+Text+Message+Non-Registered";
hbx.pndef="title";
hbx.lt="auto";//LINK TRACKING
hbx.lc="y";//Lower Case