User selector

User, Group, IP selectors are tracker field types used in the trackers feature to attribute items? to specific users. Adding a name to a tracker item is necessary but not sufficient to create special viewing and editing privileges - often used with User Tracker, registration tracker or Group tracker

The page Adding fields to a Tracker explains how the fields, (columns or questions) of a tracker are set up.

User Selector	associates the item field to a user by login name.
automatic feeding	default	an open selection from the whole list of usernames. N.B. do not use this feature if the user list is private.
	1	assign item to its creator - This option is necessary if you want to limit the modification of the item to it's creator and administrators.
	2	assign item to "last modified by" - the is filled up by the item creator or editor user name.
email	default	tikiwiki>=1.10
	1	a notification email is sent to the specified user each time the tracker item is modified(or created)

For instance a field with options "1" will assign the user who created the tracker item to the field
A field with option "0,1" will let the user to choose a user and to send a mail each time the item is modified (can be convenient for a "assign to field" )
The notification email contains the list of fields with the old and new values for each field that changed.

Display limitation:
tikiwiki>=1.10
If you want only display some users for a user selector field with no automatic feeding, you can checked the list you want while defining the field.

Note on how to get auto-assignment work in the TRACKER Plugin: In case it did not work as you expected, you could
(1) try to set view="user" in the plugin
(2) hide the field for everyone except for admin, and add it to the plugin's fields parameter. This works for both the group and the user selector fields. One current drawback (in Tiki5.0B1): the field labels are shown in both cases. As long as it is not fixed, one could use pretty trackers to circumvent this problem. Find more details in a related bug tracker item.