Q:

jQuery, Javascript : Javascript wrapped in jQuery(), $() - what does it mean? 

I'm having trouble understanding a type of jQuery selection, and I hope someone can explain it to me in clear terms. 
It's taken from this Stack Overflow question. 
Basically, it has the common jQuery: $( selector ). 
But inside that it has $({ y: iFrameScrollY }). 
I've never seen this before.  What does it mean to have { ... } and someVal: anotherVal inside the brackets? 
Also, please recommend a different title for this question, to make it easier for others to find it. 

A:

Wrapping plain JavaScript object inside jQuery object you can use few jQuery methods including: .data(),.prop(),.bind(), .unbind(), .trigger() and .triggerHandler(). 
Here is an example taken from jQuery.com:
// define a plain object
var foo = {foo:'bar', hello:'world'};

// wrap this with jQuery
var $foo = $(foo);

// test accessing property values
var test1 = $foo.prop('foo'); // bar

// test setting property values
$foo.prop('foo', 'foobar');
var test2 = $foo.prop('foo'); // foobar

// test using .data() as summarized above
$foo.data('keyName', 'someValue');
console.log($foo); // will now contain a jQuery{randomNumber} property

// test binding an event name and triggering
$foo.bind('eventName', function (){
        console.log('eventName was called');
});

$foo.trigger('eventName'); // logs 'eventName was called'

A:

What $({ y: iFrameScrollY }) does is wrap a jQuery selector object around the JavaScript object { y: iFrameScrollY }. 
The JavaScript object is declared { y: iFrameScrollY }, meaning it contains a property named y set to the value of iFrameScrollY.
By wrapping the object into a jQuery object one can avail of executing jQuery methods against the wrapped object. 
See this documentation for more details.