Why the teacher put the "<div>"string in a JQuery? if there is no $, it works as well.

Ok, I get it now.

In your original question you stated that it still worked without that $ sign. Are you positive that it does? Because I would think it would cause an error when you later do $overlay.show();

In your first example you're only assigning a string to the $overlay variable. The string happens to contain the opening and closing div tags but it is still only a string and it does not represent a real div element.

If you call the .show() method on this string as in $overlay.show() it should produce an error because strings do not have a show method. This method is part of jQuery and can only be called on jQuery objects.

In the second example with the dollar sign and parentheses you are passing in a html string into the jQuery constructor. This will take the string and create an html div element and then wrap it in a jQuery object. Now all of jQuery's methods are available to use on this object.

$overlay.show(); now works because $overlay is storing a jQuery object and we can call the show() method on that.

Let me know if that clears it up for you.