Javascript Help – Google Maps API3 Coding

I am trying to be cleverer than I need to be, and come across some code which I don’t understand and hoping someone can shed some light. I have created the code below which is meant to show the location of potential ice-cream parlors in the North of England. I can get them to individually display if I type the same code 5 times, but want to make it cleaner than that. Google uses the following – but do not understand what the i++ stuff means (and obviously Google doesn’t help!) can someone shed some light, or point me in the direction of a good resource?

 for (var i = 0; i < locations.length; i++) {

var city = locations;

var myLatLng = new google.maps.LatLng(city[1], city[2]);

var marker = new google.maps.Marker({

position: myLatLng,

map: map,

shadow: shadow,

icon: image,

shape: shape,

title: city[0],

zIndex: city[3]

});

Where this is the full code:

src="http://maps.googleapis.com/maps/api/js?key=AIzaSyBdLpdNtBopewQfcN08ywhMcotCTS5AmOQ&&sensor=false">