Admin vs firstname and lastname I've been using OS X since Lion. I'm a sole user of my Mac.

When I log into the Mac, I log in as Admin. Also, in System Preferences, under Users &amp; Groups, the Current User is listed as Admin. However, in Finder, under /Users, there's a folder with a cottage icon on it, named my firstname and lastname

Also, when I run get_current_user() in PHP (inside a XAMPP installation), I get my firstname and lastname


What's the relationship between Admin and firstname and lastname ? Are they the same? 
Why is it that Mac thinks the current user is Admin , but PHP thinks that the current user is my firstname and lastname?
Under System Preferences, why isn't my firstname and lastname listed anywhere?
What's the significance of Users listed in the Users folder? Are they different than users listed in System Preferences under Users &amp; Groups?
Does the concept of a unix-like root account factor in anywhere here?
OS X uses a short user name and a long user name.

The short name is the home folder shown in /Users/xxxxx and the long name is only shown for programs and settings that know to request the long name to display. Any where you get to enter a user name, you can choose to use either the short or long name.

To see this in practice, you can either use terminal:

whoami
whoami | id


The first will print your short name and the second shows your ID and your user numbers and internal accounting.

This is covered in several Apple support articles - best being: http://support.apple.com/en-us/HT201548

I would recommend you make a back up and have someone to check your work if you try changing the short name. It can cause old backups to get erased (since the new folder gets backed up and doesn't "save space" like other Time Machine backups do) and can cause your account to not work where you'd need to reset the setup manually and create a third admin account to patch things up.