| register_new_user() | Handles registering a new user. |
| wp_create_user() | A simpler way of inserting a user into the database. |
| wp_delete_user() | Remove user and optionally reassign posts and links to another user. |
| wp_insert_user() | Insert user data into the database. Create/update a user. |
| wp_new_user_notification() | Notifies by email the site administrator about new user registration, and sends the user an email with a login and password. |
| wp_update_user() | Update a user data in the database. Work with both tables wp_usermeta and wp_users. |