Why do I have to use $(this)? [duplicate]

Answer 1

• $() is the jQuery constructor function
• this is a reference to the DOM element of invocation

So basically, you're turning a DOM reference into a jQuery object

In your example, you could also use

listItems.each(function(index, element){
   $(element).css({
   });
});

..since .each() will pass both, index + element in its callback.