When we install wordpres by default 11 tables are generated in database:

1.wp_commentmeta:It contains meta information about comments.It has four fields meta_id, comment_id, meta_key, and meta_value. Each meta_id is related to a comment_id. Ex :it contain inforamtion whether comment is approved or pending

2.wp_comments: It contains author name who commented, url, email, comment, etc.

3.wp_links:It maintain blogrolls

4.wp_options: It contains site url, admin email, default category, posts per page, time format etc.. This table is used by number of WordPress plugins to store plugin settings.

5.wp_postmeta:It contains meta information about the post like custom fields

6. wp_post:It contains information about all posts type in wordpress.

7. wp_terms:Each term information ie tags or categories information are stored in this tables.

8. wp_term_relationships:It contain inforamtion about which post is in which category.

9. wp_term_taxonomy:It contains information about which term is category and which term is tag in wordpress.

10.wp_users:It contains information about wordpress registered users ie user name,user email,user password.

11. wp_usermeta: Contains meta information about users like contact information of user and all other meta data about registered users.