nth-child_html/css_WEB-ITnose について質問する

<style>.formtabs .panel { display: none; }.formtabs .panel:first-child { display: block; }.formtabs input[name="tabs"]:checked ~ .panels .panel { display: none; }.formtabs input[name="tabs"]:nth-of-type(1):checked ~ .panels .panel:nth-child(1),.formtabs input[name="tabs"]:nth-of-type(2):checked ~ .panels .panel:nth-child(2),.formtabs input[name="tabs"]:nth-of-type(3):checked ~ .panels .panel:nth-child(3) { display: block; }</style><div class="formtabs">    <input id="one" name="tabs" type="radio" checked>    <input id="two" name="tabs" type="radio">    <input id="three" name="tabs" type="radio">    <div class="panels">        <form method="post" action="" class="form">        <!-- <input type="hidden" name=""> -->        <div class="panel">11</div>        <div class="panel">22</div>        <div class="panel">33</div>                </form>    </div>            </div>