[thelist] <thead> vs. <th>?

Mike Combs thelist at lists.evolt.org
Mon Apr 8 20:32:01 2002 

I'm trying to be a good citizen, but I just don't see the difference here.

When should I use

<thead>
   <td>col1</td>
   <td>col2>/td>
</thead>

And when should I use
<tr>
   <td>col1</td>
   <td>col2</td>
</tr>

Thanks in advance,

...mike