preg_match

[slindstr]

I've got what I hope is a simple question. I found some code online at http://icant.co.uk/articles/phpthumbnails/ and I don't understand one of the parameters for the following code:

function createthumb($name,$filename,$new_w,$new_h){
	$system=explode('.',$name);
	if (preg_match('/jpg|jpeg/',$system[1])){
		$src_img=imagecreatefromjpeg($name);
	}
	if (preg_match('/png/',$system[1])){
		$src_img=imagecreatefrompng($name);
	}

In the if-statements, what is $system[1]?

PHP gives the following definition for preg_match:

int preg_match ( string pattern, string subject [, array &matches [, int flags [, int offset]]] )

Would $system[1] be the image whose extension I am comparing?

Thanks
Steve