User insertion/removal (category)

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()

Creates a WordPress user in the Database.

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.