Alliance battle team/ally chat

Disclaimer: Search function has been disabled due to server overload, and a quick search resulted in nothing. *dons a justified flame-proof jacket*

Doing 12 vs 12 recently has confused me on something. I keep getting messages from people talking in 'ally' chat. I have been unable to find this 'ally' chat, so I talk in team.
Trying to apply some logic to the situation has only confused me more, but has given me a plausible explanation. Especially since I noticed that some of the names (i.e. the people on my team of four) don't have 'ally' in brackets.

Is the '(ally)' just to signify that they aren't on my team of four, but they are on the team of 12?
If so, does 'team chat' send to everyone in the team of 12, or just the team of 4? (If the former, how would I toggle team of 4 and team of 12? If the latter, how do I engage the team of 12 chat?)

If it has (ally) then its someone from the other 2 teams of 4 talking to you or someone else in team chat, when your team of 4 talks to you in team chat you don't get an (ally) thingy. If you talk in team chat ppl on your team will not get the (ally) thing but will still hear you, and ppl on the other teams of 4 will hear you but next to your name will be the (ally.)