Can PHP-guru explain this simple line ot code to me?

[acinau]

There is an opening tag <?php
In the block, two variable are set
Then an if() followed by the closing tag ?>, If true, then what? If false, then what?

<?php
/**
 * A lot of commentary
 */
$options        =  get_theme_options();
$current_layout = $options['theme_layout'];

if ( 'content' !== $current_layout ) :
	?>
... lot more lines of codes follows...

[phdr]

The code is using the alternate control structure syntax - PHP: Alternative syntax for control structures - Manual

Everything after the closing ?> tag, up to the next opening <?php tag with an elseif():, else:, or endif; is part of that if(): statement’s logic.