cross domain jquery ajax request

I am sending ajax request to a url http://json-cricket.appspot.com/score.json by the code

var url="http://json-cricket.appspot.com/score.json";
$.get(url, function (data) {
    console.log(data);
}, 'json');

and this is not working, but if I add '?callback=?' to the url, then it will work. i.e.

var url="http://json-cricket.appspot.com/score.json?callback=?";
$.get(url, fun开发者_如何转开发ction (data) {
    console.log(data);
}, 'json');

Then it will work.

Both url will give the output. Only the difference is the the latter one will wrap the results on ?(result).

For my knowledge, can anyone explain me what is happening? It was taken from here.

Any link for further study would be highly appreciable.

It is because it is a cross-domain ajax request.

For more info, you can have a look at the wikipedia article http://en.wikipedia.org/wiki/JSON#JSONP