跨域的jQuery Ajax请求

我发送Ajax请求的URL http://json-cricket.appspot.com/ score.json 由code

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');

和这是行不通的，但如果我加上'？回调=？的网址，然后它会奏效。即。

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, function (data) {
    console.log(data);
}, 'json');

然后，它会正常工作。

Then it will work.

这两个网址会给输出。只是不同的是后者将包裹的结果对？（结果）。

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

有关我的知识，任何人都可以解释我发生了什么事？它是从这里 。

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

任何一个环节做进一步的研究将是非常美联社preciable。

Any link for further study would be highly appreciable.