Help with queries / eval() / templates

[Oreamnos]

I am writing some of my own pages and have a simple question regarding the interaction of the script and the templates.

i have this on test.php

PHP Code:

// Get some really valuable highly sought after information
$sql = $DB_site->query("
    SELECT * FROM " . TABLE_PREFIX . "table_name"
);
    
while ($row = $DB_site->fetch_array($sql)) {

    eval('$not_sure_what_this_is .= "' . fetch_template('MY_TEMPLATE') . '";');

} 


and my template is basically

<tr>
<td>$row[field1]</td>
<td>$row[field2]</td>
</tr>

so when the template is called the variables such as $row[field1] are printed to the page. But what is $not_sure_what_this_is? What does it do? Where can I use it? Is it necessary?

Thanks,
eric