php 中section的问题

Question

<table width="100%" border="0" cellspacing="1" cellpadding="4">
                    <tr>
                      <td width="21%" bgcolor="#eeeeee" class="m3">{l}地点{/l} </td>
                      <td width="79%" bgcolor="#FFFFFF" class="m3">
                        <table width="100%" border="0" cellspacing="1" cellpadding="1">
                          <tr>
                            <td valign="bottom"> <font class="m3">{l}路线{/l} </font> </td>
                            <td valign="bottom"> <font class="m3">{l}名称{/l} </font> </td>
                          </tr>{section name="ix01" loop=$site_code_loop}
                          <tr>
                            <td> <input type="text" name="site_code{$smarty.section.ix01.iteration}" value="{$site_code[ix01]}" size="20" maxlength="20" style="ime-mode:inactive"> </td>
                            <td> <input type="text" name="site_name{$smarty.section.ix01.iteration}" value="{$site_name[ix01]}" size="80" maxlength="100"> </td>
                          </tr>
{/section}                        </table>请问一下，$site_code_loop，{$smarty.section.ix01.iteration}这几个变数都是什么作用，谢谢大家了。