La balise <button>

<form action="">
     <fieldset>
          <legend>Informations sur vous</legend>
          <label for="description">Description</label> : <br />
          <textarea rows="10" cols="10" name="maDescription" id="description"></textarea><br /><br />
          <button>Valider le <strong>formulaire</strong></button>
     </fieldset>
</form>