MySQL EXPLAIN Explained

id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	<subquery2>	NULL	ALL	NULL	NULL	NULL	NULL	NULL	100.00	NULL
1	SIMPLE	film	NULL	ALL	PRIMARY	NULL	NULL	NULL	1000	0.10	Using where Using join buffer (hash join)
2	MATERIALIZED	category	NULL	ALL	PRIMARY	NULL	NULL	NULL	16	10.00	Using where
2	MATERIALIZED	film_category	NULL	ref	film_category_pk film_category_category_id film_category_film_id	film_category_category_id	1	sakila.category.category_id	62	100.00	NULL