Information schema is metadata about MySQL. We can obtain useful information from it. For example, I get current auto increment values by following SQL.
SELECT t.table_name, t.auto_increment FROM information_schema.tables AS t WHERE t.table_schema = 'your_db' ORDER BY t.table_name;
+-------------------------------------+----------------+ | table_name | auto_increment | +-------------------------------------+----------------+ | blog_categories | 4 | | blog_posts | 4 | | blog_post_categories | 4 | | blog_post_comments | 1 | | images | 7 | +-------------------------------------+----------------+
INFORMATION_SCHEMA database has much more useful tables like COLUMNS, GLOBAL_VARIABLES and so on. It's good to use it when you want to know much about MySQL.