title: Confused on how a JSONP request works
body: <p>I am having trouble understanding the details of how a jsonp request works. I have read several sources including the wiki on jsonp and am still very confused on how the callback actually gets a hold of the function returned from the server when a jsonp call is made. For example, in the wiki, the source of the request is set as:</p>
  
  <pre><code>src="http://server2.example.com/RetrieveUser?UserId=1234&amp;jsonp=parseResponse"
  </code></pre>
  
  <p>What exactly does jsonp = parseResponse actually do/mean?? Then they go on to say that the payload is:</p>
  
  <pre><code>parseResponse({"Name": "Foo", "Id" : 1234, "Rank": 7});
  </code></pre>
  
  <p>How does this work? I am confused on the whole callback functionality. The function name parseResponse is passed to the server and somehow the data returned becomes parameters to this function? Can someone please clearly explain exactly how data is retrieved/used from a jsonp request?</p>