What jquery / javascript files to define $? : I want to make a simple sliding Div over another div.
This Fiddle (http://jsfiddle.net/cf7u73pn/1/) is exactly what i want to make, but since i'm a noob in this world of coding, i get the warning 'Uncaught ReferenceError: $ is not defined' after copying the codes to my own files.

    <div class="hidden" id="slide">INFORMATION ABOUT IMAGE APPEARS ON CLICK</div> 
    <div class="image"><br>THERE'S A NICE IMAGE HERE</div>

    $(document).ready(function() {$('#slide').click(function() {
    var hidden = $('.hidden');
    if (hidden.hasClass('visible')) {
      hidden.animate({"top": "160px"}, "slow").removeClass('visible');
    } 
    else {
    	hidden.animate({"top": "0px"}, "slow").addClass('visible');
    }
    });
    });

I now understand that i have to link a/several (?) file(s) in my HTML head to define my $. Can someone please help me find the right files and tell me how to link these into my html?

Thank you very much!