请问怎么解释这段代码

SELECT a.shop_id, a.shop_name, b.order_id, c.order_date
FROM table_1 AS a
LEFT JOIN table_2 AS b ON a.shop_id = b.shop_id
LEFT JOIN table_3 AS c ON b.order_id = c.order_id
WHERE c.order_date >= '2018-07-01'::TIMESTAMP