What is the role of `i` in `.each(function (i) {})`?

[Eambo]

http://jsfiddle.net/6x2Nb/hello, its simple example from jQuery documentation and i'm wondering why there is \[code\] $(document.body).click(function () { $( "div" ).each(function (i) { if ( this.style.color != "blue" ) { this.style.color = "blue"; } else { this.style.color = ""; } }); });\[/code\]why there is function(i)? It equels to function() and makes no diference when exectued.Thanks