JQuery Ajax

Given below is a simple example of a jquery ajax call 

$.ajax({

    type: "POST",

    url: "http://www.w3schools.com/webservices/tempconvert.asmx/CelsiusToFahrenheit" ,

    contentType: "application/x-www-form-urlencoded",

    data: 'Celsius=75',

    dataType: "text/html", 

    success: function (msg) {

   //code to handle success goes in there

    },

    error: function (xhr, msg) {

   //code to handle failure goes in there

    }

});

Given below are their definitions

Parameter	What it means	Possible values
type	Whether to get data from or post data to the webserver	Get:  If you just need to fetch a webpage. (default) Post: If you need to send some data to the webserver and get a response based on that data. This is generally used to change the current state of the web page.
contentType	Tells the webserver what type of content is being sent by the browser	The common content  types include: application/x-www-form-urlencoded (default) application/json text/html text/plain Check here for all possible values
url	The url to make the request to.	Any web url
data	The data to be sent to the webserver	Key, value pairs
dataType	The datatype that the Jquery code would prefer to get back from the webserver.	·         xml      json      jsonp      script      html      text

To make a jquery call using JSON, you would do something like this

$.ajax({

            type: "POST",

            url: "WebServices/myWebService.asmx/MyMethod",

            contentType: "application/json; charset=utf-8",

            data: '{"param1":"' + param1+ '", "param2":"' + param2 + '"}',

            dataType: "json",

            success: function(msg) {

                 

                var jsonObj = msg.d;

                var returnParam1 = jsonObj['To'];

                var returnParam2 = jsonObj['Subject'];

                var returnParam3 = jsonObj['Body'];

            },

              error: function (xhr, msg) {              
                         //code to handle failure goes in there
                }

   }); //end of  $.ajax

Check this out on a detailed simple example on making an ajax call.