The <th> tag is used to create a header cell in an HTML table.
The text in a TH element gets more emphasis then other words, it is bold and centered.

as in

<table border=1>
  <tr>
    <th>Date</th><th>Commission</th>
  </tr>
  <tr>
    <td>01-09-2011</td><td>€65</td>
  </tr>
</table>