+ *
+ * Can update a current user or insert a new user based on whether the user's ID
+ * is present.
+ *
+ * Can be used to update the user's info (see below), set the user's role, and
+ * set the user's preference on whether they want the rich editor on.
+ *
+ * Most of the $userdata array fields have filters associated with the values.
+ * The exceptions are 'rich_editing', 'role', 'jabber', 'aim', 'yim',
+ * 'user_registered', and 'ID'. The filters have the prefix 'pre_user_' followed
+ * by the field name. An example using 'description' would have the filter
+ * called, 'pre_user_description' that can be hooked into.
+ *
+ * The $userdata array can contain the following fields:
+ * 'ID' - An integer that will be used for updating an existing user.
+ * 'user_pass' - A string that contains the plain text password for the user.
+ * 'user_login' - A string that contains the user's username for logging in.
+ * 'user_nicename' - A string that contains a nicer looking name for the user.
+ * The default is the user's username.
+ * 'user_url' - A string containing the user's URL for the user's web site.
+ * 'user_email' - A string containing the user's email address.
+ * 'display_name' - A string that will be shown on the site. Defaults to user's
+ * username. It is likely that you will want to change this, for both
+ * appearance and security through obscurity (that is if you don't use and
+ * delete the default 'admin' user).
+ * 'nickname' - The user's nickname, defaults to the user's username.
+ * 'first_name' - The user's first name.
+ * 'last_name' - The user's last name.
+ * 'description' - A string containing content about the user.
+ * 'rich_editing' - A string for whether to enable the rich editor or not. False
+ * if not empty.
+ * 'user_registered' - The date the user registered. Format is 'Y-m-d H:i:s'.
+ * 'role' - A string used to set the user's role.
+ * 'jabber' - User's Jabber account.
+ * 'aim' - User's AOL IM account.
+ * 'yim' - User's Yahoo IM account.
+ *
+ * @since 2.0.0
+ * @uses $wpdb WordPress database layer.
+ * @uses apply_filters() Calls filters for most of the $userdata fields with the prefix 'pre_user'. See note above.
+ * @uses do_action() Calls 'profile_update' hook when updating giving the user's ID
+ * @uses do_action() Calls 'user_register' hook when creating a new user giving the user's ID
+ *