通过ext.js进行ajax请求

I would like to ask a question please, I have the following code that I copied it from some source:

Ext.Ajax.request({
    url: 'http://localhost/day1/new.php',  
    method:'GET', 
    params:{format:'json'},
    success: this.log,  
    failure: this.fail,   
    scope:this   
});

I don't really understand what is the property (params) means? What value should I put in it and what it's supposed to do in the request?

I want to check whether the following JSON format is correct and that it follows the standards:

{"count":"2",
"results":{
    "result":[ {"description":"Cholet",
                "lat":"16.620974289775",
                "lng":"16.620974289775"}
    ]
} } 

Use jquery ajax json method instead of this one , it is easy to understand and implement. Check out below 2 links.

  1. http://api.jquery.com/jQuery.getJSON/
  2. http://www.9lessons.info/2009/10/json-jquery-ajax-php.html