Super Admins are upgraded Admins which cannot be banned or kicked. they can be banned if they leave the server. Super Admins may abuse their immunity to kicking and banning by doing unapproved things such as tearing down buildings or stuff like that, by using a BlowTorch (pointless since V16, "Sniper Destructo Wand" update), a destructo wand wand that has unlimited range, or just a normal Destructo Wand.Super Admin can also Admin/De-admin people, as this could be very abusive in cases.Super admin are abreviated SA commonly, or SuperA, less comonly, or Sadmin, more commonly that SuperA. There is no longer a way to be a Super Admin since Return To Blockland went down.
EDIT: There have been a few RTB remakes out there that allow you to auto-admin and auto-super admin people.