When an admin views a user profile in the admin area, there is a panel on the Profile tab called Account Information.
This panel provides details into a users creation and certain activity.
Note: The details in this panel cannot be edited, but contains helpful information on activity as shown and explained below.
Created by: this shows you who the user was created by and some details on how (e.g upload)
Created: this is the date the users profile was created
Updated: when their users profile was last updated
Last login: when the user last logged in