API TYPE ChatTypeId

From WoWDev

These are the chat types used by SendChatMessage("msg"{,"type"{,"lang"{,"channel"}}}).

Values

"SAY" 
Speech to nearby players (/say).
"EMOTE" 
Text emote to nearby players (/em) (Use DoEmote("action") for voice emotes)
"YELL" 
Yell to not so nearby players (/yell).
"PARTY" 
Message to party members (/p)
"GUILD" 
Message to guild members (/g)
"OFFICER" 
Message to guild officers (/o)
"RAID" 
Message to raid members (/raid)
"WHISPER" 
Message to a specific other player (/whisper) - Player name provided as channel.
"CHANNEL" 
Message to a specific chat channel (/1,/2,...) - Channel number provided as channel