Ok, I will go through the different chat channels for you.
 
Name of channel    Command   Usage
Town chat               /tc              Talking to town members
Nation chat             /nc              Talking to nation members.
Global chat             /ch g            Lets you talk to everyone online
Local chat               /ch l             Lets you talk to close friends.
Mining chat             /ch mining    Only available in the mining world, lets you talk to people in that world also
Ender chat              /ch en          Only available in the ender realm, lets you talk to people in that realm also.
Nether chat             /ch n            Only available in the Nether realm, lets you talk to people in that realm also.
Events chat             /ch e             Only available in the Events world, lets you talk to people in that world also.



These are the chat channels available at your rank.