Whether the user with the specified ID is active or not.
When a different user is selected, this state will become inactive.
When returning to the specified user, the state will become active again.
Note that each user account has it's own set of apps, so to detecting each user becoming active would require Tasker to be installed under each account.
In other words, it only makes sense to specify the user ID of the user under which the current Tasker install is running.
The administrator (first user) ID is usually 0, the action Test System can be used to determine other user IDs.
This state requires Android 4.2+.