To return the username of a user
The function tells you the username of the current or a user.
userName()To return the username of the current user.
Result: Steve Rogers (if Captain America is processing the function and has this on file in his profile)
userName(myUser)To return the username of a given user.
Select Captain America in the user field Superhero.
Result: Captain America
(if Captain America is selected in the Superhero field and that is the display name on file)