how does it work?

[vuiveclub]

hello all,
i've opened some code (ex. vbplaza.php) and see something like

// check if it should do the richest/most sold scripts
if ($_REQUEST['do'] == 'main')
{
	// always show some history on the main page
	$show['history'] = true;

	// always show it on the main page
	$show['richestmostsold'] = true;
}

I don't understand using $show['history'] = true; or $show['richestmostsold'] = true;

Could some one teach me about this, how to write, how to use?
Thank so much, sorry for my bad English