Trade chat
Trade chat, also known as the trade channel, is a common chat channel that only works in capital cities. It is linked across all such cities on a single realm (with connected realms sharing a trade chat). This channel is intended for buying, selling, and trading of items and services, but it is often used for general chit-chat, gold spamming and guild recruitment as well.
The channel is also heavily used instead of the LookingForGroup channel to recruit players for group activities, particularly instance types without an automated group finder. As of Mists of Pandaria those types are heroic scenarios, raids beyond the Raid Finder level, rated battlegrounds and arenas. Other frequent objectives include world bosses, PvP raids, achievements, reputation or item farming, and premade battleground groups. Prior to patch 3.3.0 and the Dungeon Finder, the channel was also heavily used for recruiting players to 5-man dungeonss.
Players in the same faction (Horde or Alliance) will only see messages sent from players of the same faction, whether they are in a sanctuary, an allied capital, or an enemy capital.
Trade is usually channel 2; to send a message in this channel, type /2 in the chat input box and press the spacebar, then type your message and press enter.
Patch 9.2.7 introduced a new Trade (Services) channel for searching or advertisement of services like raiding, dungeon or PvP activities while keeping the trade chat to the traditional buying and selling of items and professions.