In game if you open Team Chat by pressing the key "u" and first type @ then your message this will send a message only visable to admins which can be used if you have questions or are in need for assistance. You are able to send messages in admin chat but you are not able to view the admin chat yourself so they will reply in a different way.
Example:
Click the key "u"
Team Chat:'@'Can an admin help me out?
This will then pop up in chat visable to all admins in game.
Example:
Click the key "u"
Team Chat:'@'Can an admin help me out?
This will then pop up in chat visable to all admins in game.