An Administrator can edit a user on this page (or a user can edit his own profile): change his username, first/last names, email, phone, change his password etc.
You can also enable/disable email notifications for a user, and (if a user is a technician) enable/disable "new ticket" notifications sent to technicians (this also controls "another tech takes a ticket" notification if you have them enabled).
You can mark a user "out of office", which will simply display a small "away" icon in user profile, the user-info popup and in the "agents" drop-down list when someone tries to assign a ticket to the user.
You can also override the system-default language for the user or override the system-default timezone - this way the main ticket grid and the ticket page will display times in user-specific timezone. Other pages (like reporting etc) will still use the system-default timezone.
An Administrator can also edit user's permissions: make him administrator, a technician, or a manager (or just keep him a regular user).
Users can upload their own avatar images, if avatars are enabled in your Helpdesk. The avatar image should be in a form of square - 100x100 pixels and 50Kb max. If users don't upload custom avatar images, Helpdesk will try to obtain the image from Gravatar.com using user's email address. If you are using Windows auth, helpdesk will try to get user avatars from Active Directory.