May I know what is the difference for the script below (With $when vs without $when for ajaxRequest )

$.when(ajaxRequest("GET", "Api/Filter/Country", null, true)).done(function (data) {
    return data;
});

And below

ajaxRequest("GET", "Api/Filter/Country", null, true).done(function (data) {
        return data;
    });

Main Function

ajaxRequest: function (type, url, data) {
            var options = {
                dataType: "json",
                contentType: "application/json",
                cache: false,
                type: type,
                data: data ? ko.toJSON(data) : null
            };

            var antiForgeryToken = $("[name='__RequestVerificationToken']")[0].value;
            if (antiForgeryToken) {
                options.headers = {
                    'RequestVerificationToken': antiForgeryToken
                }
            }
            return $.ajax(url, options);
        }