MySQL/Database Help

I'm wondering if someone can explain this code a little for me the table is actualy jos_ezrealty I can understand where the defined variable for that is coming from however I'm a little confused where the a.* is reference and the letter in front of the code. thanks so much

   

$query = "SELECT a.*, u.mid AS mid, u.dealer_name AS dealer_name, u.dealer_company AS dealer_company, u.dealer_email AS dealer_email, 
	u.dealer_phone AS dealer_phone, u.dealer_mobile AS dealer_mobile, u.dealer_sms AS dealer_sms, u.show_sms AS show_sms, 
	u.dealer_image AS dealer_image, u.dealer_type AS dealer_type, u.logo_image AS logo_image, u.published AS dealerpublished, 
	p.mid AS amid, p.dealer_name AS adealer_name, p.dealer_company AS adealer_company, p.dealer_phone AS adealer_phone, 
	p.dealer_mobile AS adealer_mobile, p.dealer_sms AS adealer_sms, p.show_sms AS ashow_sms, p.dealer_image AS adealer_image, 
	p.dealer_type AS adealer_type, p.logo_image AS alogo_image, p.published AS adealerpublished, 
	q.username AS user1, r.username AS user2 FROM #__ezrealty as a"
	. "\n LEFT JOIN #__ezrealty_profile AS u ON u.mid = a.owner"
	. "\n LEFT JOIN #__ezrealty_profile AS p ON p.mid = a.assoc_agent"
	. "\n LEFT JOIN #__users AS q ON q.id = a.owner"
	. "\n LEFT JOIN #__users AS r ON r.id = a.assoc_agent"
    . "\n WHERE a.published = '1' AND a.id = $id";
    $database->setQuery( $query );
    $rows = $database->loadObjectList();
	$row = $rows[0];

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