初学asp.net,对于sdk文档中的一行代码不理解,请指点!

[C#] 
<%@ Page Language="C#" AutoEventWireup="True" %><html>
   <script runat="server" >
  
      void Page_Load(Object sender, EventArgs e)
      {         // Create the HtmlTable control.
         HtmlTable table = new HtmlTable();
         table.Border = 1;
         table.CellPadding = 3;         // Populate the HtmlTable control.
          
         // Create the rows of the table.
         for(int rowcount=0; rowcount<5; rowcount++)
         {
            HtmlTableRow row = new HtmlTableRow();
            
            // Create the cells of a row. 
            for(int cellcount=0; cellcount<4; cellcount++)
            {
               HtmlTableCell cell;               // Create table header cells for first row.   ???我理解为:为第一行创表标头,与下面的"th"有什么关系?
               if(rowcount <= 0)
               {
                  cell = new HtmlTableCell("th");          ???为什么要这样做,什么意思
               }
               else
               {
                  cell = new HtmlTableCell();
               }               // Create the text for the cell.
               cell.Controls.Add(new LiteralControl(
                   "row " + rowcount.ToString() + ", " + 
                   "column " + cellcount.ToString()));               // Add the cell to the Cells collection of a row. 
               row.Cells.Add(cell);
               
            }            // Add the row to the Rows collection of the table.
            table.Rows.Add(row);
          
         }
 
         // Add the control to the Controls collection of the 
         // PlaceHolder control.
         Place.Controls.Clear();
         Place.Controls.Add(table);
         
      }
  
   </script>
  
<body>   <form runat="server">
  
      <h3> HtmlTable Example </h3> 
  
      <asp:PlaceHolder id="Place" runat="server"/>
  
   </form></body>
</html>