explain this code please

explain this code please

I have this code but it is first time I see a selection like this in the line "var mybtn". Please any one give me a  reference or documentation to this kind of selection as I could not find any. Also please explain why tag "<button/>" was used not "<button>" or something else


  1. <!DOCTYPE html>
    <html>
    <head lang="en">
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>

    <button type="button" class="btn">Click Me!</button>


    <script src="js/jquery-2.1.3.min.js"></script>
    <script src="js/btn.js"></script>
    </body>
    </html>
  1. $(document).on('click', '.btn', function(){
       var mybtn = $('<button/>',
           {
               text: 'Click Me!',
               class: 'btn'

           });

        var parent = $("body").append(mybtn).end();
    });


Thanks