新手学习的问题

刚开始学习在入门里看到这个程序大家解释一下<html>
   <head>
 
      <link rel="stylesheet" href="intro.css">
   </head>   <body>       <center>       <form action="intro1.aspx" method="post">           <h3> 姓名：<input id="Name" type=text>           类别：<select id="Category" size=1>
                          <option>psychology</option>
                          <option>business</option>
                          <option>popular_comp</option>
                      </select>           <input type=submit value="查找">
           </h3>
       </form>       </center>   </body>
</html>