File Manager "Advanced Search" options

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I was looking through the code for the File Manager, specifically the file search_form_advanced.php located in the elements/files folder. Near the bottom of the file on lines 326-329, I found:

<?php if ($_REQUEST['fssID'] > 0) { ?>
$('#ccm-<?php echo $searchInstance?>-advanced-search input, #ccm-<?php echo $searchInstance?>-advanced-search select, #ccm-<?php echo $searchInstance?>-advanced-search textarea').attr('disabled',true);
$('#ccm-<?php echo $searchInstance?>-advanced-search select[name=fssID]').attr('disabled', false);
<?php } ?>

I'm still a bit new to php and don't exactly know what these reference- what do they do? If the "disabled', false/true" phrases were changed between true or false, what would that affect?

Thanks in advanced,